Nuclei in the Cosmos (NIC XVII)
Nuclei in the Cosmos (NIC) is the most important international meeting in the field of nuclear astrophysics. It brings together nuclear experimentalists, nuclear theorists, astronomers, theoretical astrophysicists, cosmo-chemists, and others interested in the scientific questions at the interface of nuclear physics and astrophysics. These questions concern, for example, the origin of the elements in the cosmos and the nuclear reactions that occur in the Big Bang, in stars, and in stellar explosions.
The NIC 2023 abstract submission is closed now (deadline: Wednesday, May 31).
Discussion Topics
- Nuclear reaction rates and stellar abundances
- The s-process
- Nuclear properties for astrophysics
- High-density matter
- Novae and X-ray bursts
- Type Ia supernova and the p-process
- Core-collapse supernovae, mergers and the r-process
- Underground nuclear astrophysics
- The early universe
- Galactic evolution
- Radioactivity and meteorites
- Stellar modelling
- Others (new facilities, instruments, tools, etc)
The school for NIC XVII for graduate students and young postdocs will be held at the Institute for Basic Science, Sep. 11-15. The school will provide lectures on basics and the current subjects in nuclear astrophysics, from theories to experiments and observations.
In addition, the NIC-XVII Pre-workshop will be held from September 15-16, 2023 at Dasom Hall (Room #19105) in the Computer Science building (Cheon san gwan) at Soongsil University in Seoul, Korea. The workshop will involve discussions on various topics in (nuclear) astrophysics, astronomy, cosmological chemistry, and other related fields, fostering a relatively informal and open environment.
NIC XVII is organized by the Center for Exotic Nuclear Studies (CENS) and the Rare Isotope Science Project (RISP) at Institute for Basic Science. NIC XVII is also supported by Korean institutions and the international research centers in the world.
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Reception
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Opening
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Opening & WelcomeSpeaker: Kevin Insik HAHN (Center for Exotic Nuclear Studies, IBS)
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Congratulatory AddressSpeaker: Do Young NOH (Institute for Basic Science)
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The s-process
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Questions in Experimental Nuclear Astrophysics
Nuclear Astrophysics is low energy reaction physics – with stable and radioactive nuclei. The goal of the field is to understand critical reaction cross sections at stellar energies which are typically not directly accessible by experiment. The reaction rates therefore depend on reliable extrapolation of the reaction rates towards the stellar energy regime. A number of near threshold effects may cause unexpected changes in the reaction cross sections at those conditions. I will present a number of these cases and will discuss how such changes may impact the reaction rates and the corresponding stellar observables.
Speaker: Prof. Michael WIESCHER (University of Notre Dame) -
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New constraints on the $^{13}$C$(\alpha,n)^{16}$O reaction
Neutron production for the slow neutron capture process ($s$-process) is dominated by $(\alpha,n)$ reactions on light nuclei during stellar helium burning. Chief amount these is the $^{13}$C$(\alpha,n)^{16}$O reaction, whose low energy cross section is enhanced by the presence of broad resonances and subthreshold states. Experimental measurements have been reported recently at both the LUNA and JUNA underground facilities, reaching to unprecedentedly low energies. These measurements have verified $R$-matrix extrapolations, constrained by transfer reaction determinations of the dominant subthreshold resonance strength, that the cross section is lower than previous above ground measurements indicated. To further reduce the uncertainty we report measurements of the differential cross section of the $^{13}$C$(\alpha,n)^{16}$O reaction, which extend from laboratory $\alpha$-particle energies of 0.8 to 6.5 MeV in approximately 10 keV energy steps at 18 unique angles between 0 and 160$^\circ$, resulting in over 700 distinct angular distributions. These measurements are the first accurate differential cross section measurements of this reaction below 1 MeV. We use these differential data to augment the previous state-of-the-art $R$-matrix fit of the low energy $^{13}$C$(\alpha,n)^{16}$O reaction and use Bayesian uncertainty estimation to demonstrate that the differential data decreases the uncertainty by a factor of two, from $\approx$10\% to $\approx$5\% over the energy region of astrophysical interest.
Speaker: Richard DEBOER (University of Notre Dame) -
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New determination of $^{17}$O+$\alpha$ reaction rates and impact on the s-process in metal-poor rotating massive stars
The efficiency of the weak s-process in low metallicity rotating massive stars depends strongly on the ratio of the reaction rates of the two competing $^{17}$O($\alpha$,n)$^{20}$Ne and $^{17}$O($\alpha$,$\gamma$)$^{21}$Ne reactions, which impacts the poisoning effect of $^{16}$O that consumes the neutrons released by the $^{22}$Ne($\alpha$,n)$^{25}$Mg reaction [1] .
However, the reaction rates of these two competing reactions are poorly known in the astrophysical energy range of interest due to the lack of spectroscopic information (partial widths, spin-parities) on the relevant states in the compound nucleus $^{21}$Ne. Therefore, the $\alpha$-widths of these states were determined experimentaly for the first time by measuring their $\alpha$-spectroscopic factors using the $\alpha$-transfer reaction $^{17}$O($^7$Li,t)$^{21}$Ne. The latter was performed at MLL-Munich using the high-energy resolution magnetic spectrometer Q3D [2].
The measured differential cross sections of the different populated states as well as their analysis using the DWBA formalism will be presented, along with the obtained $\alpha$-spectroscopic factors and $\alpha$-widths of the relevant states in $^{21}$Ne. The new $^{17}$O($\alpha$,n)$^{20}$Ne and $^{17}$O($\alpha,\gamma$)$^{21}$Ne reaction rates calculated using the obtained $\alpha$-widths will be presented and compared with previous evaluations. The new rates favour neutron recycling through the $^{17}$O($\alpha$,n)$^{20}$Ne reaction and suggest an enhancement by more than 1.5 dex of the weak s-elements between zirconium and neodymium in metal-poor rotating massive stars.[1] A. Choplin, R. Hirschi et al. Astron. Astrophys. 618, A133 (2018)
[2] F. Hammache, P. Adsley, L. Lamia et al., submittedSpeaker: Faïrouz HAMMACHE (IJCLab-Orsay)
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4
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Coffee break
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The s-process
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The s-process in AGB stars
About half of the solar abundance of elements heavier than iron are made by the slow neutron capture process (s-process) occurring in low and intermediate-mass asymptotic giant branch (AGB) stars. Elements are mixed from the core to the surface and then expelled into the interstellar medium through strong stellar winds. In comparison to the rapid neutron capture process, modelling the s-process has presented fewer difficulties owing to the fact that most of the nuclei involved are near the valley of stability, and we observe stars enriched in heavy elements produced by the s-process. However, many important uncertainties still remain including the mechanism leading to the formation of $^{13}$C pockets and the details around mixing in AGB stars. There is an increasing wealth of observational data that is being used to constrain s-process modelling in AGB stars. In recent years the main improvements to these observations have come from accurate distance estimates owing to Gaia. In this talk I will review the current status of theoretical models of the s-process in AGB stars. I will also provide an update on observations, highlighting results from Galactic AGB stars, which may provide a constraint on the minimum stellar mass required for a star to produce s-process elements. I will also briefly touch on the intermediate neutron capture process (or i-process) and show evidence that this process occurred in the early Galaxy. I will show that a potential site is AGB stars experiencing proton ingestion episodes during convective He-shell burning but other sites exist, and are still debated.
Speaker: Amanda KARAKAS (Monash University) -
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The s process - nuclear physics aspects
About half of the elements heavier than iron are produced in rather quite stellar environments during long exposures of seed material with neutrons. The interplay between neutron captures and beta-decays enables the production of all elements between iron and bismuth. This process is called slow neutron capture process, or s process.
Radioactive isotopes on the s-process path can act as branch points. The anaylsis of the branching ratios allows conclusions about the stellar conditions during the process. However, it requires the knowledge of the corresponding reaction rates as a function of the environmental parameters. The most important reacions are neutron captures and beta-decay rates.
I will present the basic ideas of the s process nucleosysnthesis, discuss the latest developments constraining the reaction rates and give an outlook towards possible future developments.
Speaker: Rene REIFARTH (Goethe University Frankfurt (DE)) -
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New s-process yields and surface abundances from asymptotic giant branch models
Theoretical stellar nucleosynthesis calculations allow direct comparison between predicted stellar abundances and observations, as well as interpretation of the isotope composition of meteoritic components. Our computational method for calculating predictions for stellar abundances from AGB stars involves two steps: first, the evolution of the stellar structure is calculated by the Stromlo stellar structure evolution code[1], and second we feed the stellar structure inputs (T, $\mathrm{\rho}$, and convective velocities) into the dppns45 post-processing code[2] that solves simultaneously the abundance changes due to nuclear reactions and to convective mixing for 328 nuclear species. In this study we upgrade the reaction network of the post-processing code to account for the temperature and density dependence of the radioactive decay and electron captures following the compilation of NETGEN (Nuclear NETwork GENerator)[3], and a large number of neutron-capture rates based on ASTRAL (ASTrophysical Rate and rAw data Library)[4], which contains re-evaluated experimental MACS of several neutron-capture reactions. The results of the work are new theoretical s-process yields and surface abundances for AGB stars with initial masses 2.5, 3 and 4 $\mathrm{M_{\odot}}$ for half-solar and double-solar metallicity, and 2 $\mathrm{M_{\odot}}$, 3 and 4 $\mathrm{M_{\odot}}$ for solar metallicity. We compare our predictions with the previous model predictions, predictions from the FRUITY database[5], and isotopic ratios measured in presolar SiC grains.
[1] Lattanzio, J. C. 1986, ApJ, 311, 708
[2] Cannon, R. C. 1993, MNRAS, 263, 817
[3] Xu, Y., Goriely, S., Jorissen, A., Chen, G. L., & Arnould, M. 2013, A&A, 549, A106
[4] Reifarth, R., Erbacher, P., Fiebiger, S., et al. 2018, European Physical Journal Plus, 133, 424
[5] Cristallo, S., Straniero, O., Gallino, R., et al. 2009, ApJ, 696, 79Speaker: Balázs SZÁNYI (Konkoly Observatory, CSFK; University of Szeged)
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Lunch break
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Underground nuclear astrophysics
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JUNA investigation of star evolution in deep underground laboratory
The Jinping Underground experiment for Nuclear Astrophysics (JUNA) has leveraged the ultralow background of the CJPL to conduct experiments aimed at directly studying crucial reactions occurring at relevant stellar energies during the evolution of stars. In 2020, JUNA successfully commissioned an mA level high current accelerator based on an ECR source, as well as BGO and $^3$He detectors. These advancements enabled JUNA to perform direct measurements of several key reactions, including $^{25}\rm{Mg}(p,\gamma)^{26}\rm{Al}$, $^{19}\rm{F}(p,\alpha\gamma)^{16}$O, $^{19}\rm{F}(p,\gamma)^{20}\rm{Ne}$, $^{13}\rm{C}(\alpha,n)^{16}$O, $^{12}\rm{C}(\alpha,\gamma)^{16}$O, and $^{18}\rm{O}(\alpha,\gamma)^{20}$Ne with improved precision and across a wider energy range, closer to the Gamow window. These experiments provide valuable insights into the astrophysics implications (neutron source, F and Ca over production etc.) with their precise reaction rates.
1. Liu W P et al., Sci. China Phys. Mech. 59(2016)642001
2. Zhang L Y et al., Phys. Rev. Lett. 127(2021)152702
3. Su J et al., Sci. Bull. 67(2022)125
4. Gao B et al., Phys. Rev. Lett. 129(2022)132701
5. Zhang L Y et al., Nature 610(2022)656
6. Wang L H et al. , Phys. Rev. Lett. 130(2023)092701Speaker: Prof. Weiping LIU (SUSTech/CIAE) -
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Nuclear Astrophysics in underground laboratories: the LUNA experiment
In nuclear astrophysics, a crucial aspect is understanding the thermonuclear reactions that power the stars and lead to the synthesis of chemical elements. At astrophysical energies, the cross section of nuclear processes is significantly reduced by the Coulomb barrier, making direct measurements challenging. In addition, the low value of cross sections often hinders their measurement on Earth's surface, necessitating extrapolations. To overcome this problem, the Laboratory for Underground Nuclear Astrophysics (LUNA) is located under the Gran Sasso mountain. This position reduces the effects of cosmic-ray background and allows cross sections investigations at energies close to the Gamow peak in stellar scenarios. The LUNA-50kV and LUNA-400kV accelerators have been used to directly measure many crucial reactions involved in hydrogen burning at astrophysical energies, and work continues with the installation of a 3.5MV machine that will explore helium and carbon burnings. Due to this progress, there are currently running projects in several countries using underground accelerators. This presentation will describe the typical techniques used in underground nuclear astrophysics and review the most significant results achieved. The talk will also highlight the exciting science that can be probed with the new facilities.
Speaker: Antonio CACIOLLI (University and INFN of Padua) -
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Measurements of Proton Capture on Carbon at Astrophysical Energies
Direct measurements of the cross sections for the radiative capture reactions ${}^{12,13}\mathrm{C}(\mathrm{p},\gamma){}^{13,14}\mathrm{N}$ at energies of astrophysical interest are challenging, due to the rapidly falling cross sections towards lower energies, and for the absence of narrow resonances at low proton energies required for target characterization. The two reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA). Exploiting the low-background setup at the deep-underground location, and using different solid targets and complementary detection techniques, a comprehensive data set for energies between $E_\mathrm{c.m.} = 60\,\mathrm{keV}$ and $370\,\mathrm{keV}$ has been obtained, providing direct data on this reaction at the lowest energies to date. We will present the performed experiments, and the results for the cross sections of both reactions.
Speaker: Axel BOELTZIG (Helmholtz-Zentrum Dresden-Rossendorf (HZDR)) -
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22Ne+a measurements deep underground
The reactions 22Ne(a,n)25Mg and 22Ne(a,g)26Mg are of high importance for the formation of heavy elements in the weak s process, main s process branchings and strongly influence the Mg isotopic ratios that we can directly observe in stellar atmospheres. For an accurate astrophysical modeling, both reaction cross sections need to be known at energies far below the Coulomb barrier, where direct measurements are severely hampered due to the low event rates to be detected. Many indirect studies have probed the relevant compound nucleus energy region (> 10.6 MeV), but large uncertainties remain regarding the contributions of the various excited states to the astrophysical reaction rates.
To tackle this issue, a new campaign of direct measurements of both reactions is currently being prepared at the new 3.5 MV accelerator in the Bellotti Ion Beam facility of the INFN-LNGS deep underground laboratory. The ultra-low gamma and neutron background in combination with novel detection setups and high ion beams will greatly extend the detection sensitivity, allowing to measure much lower cross sections than previously possible. The measurement of the neutron channel using an innovative hybrid detection setup is taking place in the framework of the "SHADES" ERC grant.
We will give an overview of the state of the art and the current status of the experimental projects.Speaker: Andreas BEST (University of Naples Federico II) -
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Measurement of the low energy resonances in 22Ne(a,g) and 22Ne(a,n) reaction
The interplay and correlation between the $^{22}$Ne$(\alpha,\gamma)^{26}$Mg and the competing $^{22}$Ne$(\alpha,n)^{25}$Mg reaction determines the efficiency of the $^{22}$Ne$(\alpha,n)^{25}$Mg reaction as a neutron source for the weak $s$-process. In both cases, the reaction rates are dominated by the strength of the $\alpha$ cluster resonance at 830 keV. This plays a particularly important role in determining the strength of the neutron flux for weak and main s-process environments. We performed the measurement of the 830 keV resonance in $^{22}$Ne$(\alpha,\gamma)^{26}$Mg at the Sanford Underground Research Facility using a $\gamma$-summing detector. We confirmed the previous studies of the resonance strength and obtained a strength of $\omega\gamma$ = 35 $\pm$ 4 $\mu$eV, however the strength of the corresponding resonance in the $^{22}$Ne$(\alpha,n)^{25}$Mg still carries large uncertainties. In a new and independent study performed at Notre Dame using a stilbene crystal detector, we confirmed previous results and demonstrate that the resonance strength in the competing $^{22}$Ne$(\alpha,n)^{25}$Mg reaction channel is significantly higher.
Speaker: Ms Shahina SHAHINA (University of Notre Dame) -
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Deep underground laboratory measurement of $^{13}$C($\alpha$,n)$^{16}$O in the Gamow windows of the s- and i-processes
The $^{13}$C($\alpha$,n)$^{16}$O reaction is the main neutron source for the slow-neutron-capture (s-) process in Asymptotic Giant Branch stars and for the intermediate (i-) process. Direct measurements at astrophysical energies in above-ground laboratories are hindered by the extremely small cross sections and vast cosmic-ray induced background. We performed the first consistent direct measurement in the range of E$_{\rm c.m.}$ =0.24 MeV to 1.9 MeV using the accelerators at the China JinPing underground Laboratory (CJPL) and Sichuan University. Our measurement covers almost the entire i-process Gamow window in which the large uncertainty of the previous experiments has been reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing data sets, and provides a more reliable reaction rate for the studies of the s- and i-processes along with the first direct determination of the $\alpha$-strength for the near-threshold state.
Speaker: Dr Bingshui GAO (ON BEHALF OF THE JUNA COLLABORATION) (Institute of Modern Physics) -
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Exploring the Potential for Astrophysical Neutrino Detection at JUNO
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator detector currently under construction in an underground laboratory in South China. It is expected to complete detector construction by the end of 2023. With excellent energy resolution, a large detector volume and superb background control, JUNO will become a flagship experiment in the coming decades. Its primary aims are determining the neutrino mass ordering, and providing precise measurements on the neutrino oscillation parameters with reactor antineutrinos. As a multi-purpose neutrino observatory, JUNO has world-competitive potential on astrophysical phenomena such as diffuse supernova neutrino background (DSNB), core-collapse supernova (CCSN) neutrinos, solar neutrinos, and more. This talk will present the astrophysical potential of neutrino research at JUNO.
Speaker: Dr Jie CHENG (NCEPU)
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Coffee break
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Nuclear reaction rates and stellar abundances
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Neutron-capture reactions and heavy element nucleosynthesis
In recent years, new astronomical observations have revealed abundance patterns that cannot be explained by the classic nucleosynthesis picture. A description of the synthesis of heavy elements using only the s, r and p processes is not adequate anymore and for this reason new scenarios had to be proposed. In this talk I will focus on neutron-capture processes that involve exotic nuclei, specifically the r process and the intermediate (i) process. I will discuss possible contributions from each and, in particular, I will address uncertainties related to the nuclear physics input. Neutron-capture reactions play a major role in both processes, and I will present recent developments in providing experimentally constrained reaction rates using indirect techniques. I will share recent results from experiments at Argonne National Laboratory in the US and future experiments at the Facility for Rare Isotope Beams (FRIB).
Speaker: Spyrou ARTEMIS (Michigan State University) -
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The status and future of nuclear property experiments at CENS
Observations of astrophysical phenomena, such as the luminosity of X-ray bursts and the abundance pattern of stars, can be explained by nuclear reactions occurring in the stars. It is well known that the nuclear properties of isotopes involved in the nuclear reactions have a direct impact on stellar evolution, such as energy generation, the nucleosynthesis path, and final abundance distribution of the elements. However, because most of the key nuclei constraining the nucleosynthesis models including the rapid proton capture process (rp-process) and the rapid neutron capture process (r-process) are far from stability, our understanding of astronomical observables is still very limited due to large uncertainties in calculated properties of the nuclei and a lack of measurements with radioactive ion beams for the spectroscopic information. One recent sensitivity study, for example, shows the light curve of X-ray bursts is extremely sensitive to ($\alpha$,$p$) reactions on proton-rich radioactive nuclei, including $^{14}$O($\alpha$,$p$)$^{17}$F, $^{15}$O($\alpha$,$\gamma$)$^{18}$Ne and $^{34}$Ar($\alpha$,$p$)$^{37}$K. However, measurement of these reaction cross sections in the laboratory is challenging due to low beam intensities and short lifetimes.
In order to reduce the uncertainties, new experimental studies of nuclear properties with heavy ion radioactive beam accelerators are critical. Moreover, because most of key nuclei allowing us to explore new models of nuclear structure are far from stability, it is only possible to perform the research with powerful rare isotope beam (RIB) facilities. Recent experimental studies of nuclear properties performed by the Center for Exotic Nuclear Studies (CENS), Institute for Basic Science at will be presented as well as new device developments. Future plans on how to take advantage of the existing and new RIB facilities including RAON (Rare isotope Accelerator complex for ON-line experiment) in Korea will also be addressed.
*This work was supported by the Institute for Basic Science (IBS-R031-D1), Ministry of Science and ICT(MSIT), Republic of Korea.
Speaker: Dr Sunghoon(Tony) AHN (Center for Exotic Nuclear Studies, Institute for Basic Science) -
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Realistic fission transmission coefficients in the statistical Hauser-Feshbach compound-nucleus reaction theory
Albeit recent development of dynamical approaches to the nuclear fission phenomena has been significantly improving our understanding of this complex nuclear reaction mechanism, conventional fission models in the statistical Hauser-Feshbach theory remain the extremely simplified fission barrier model with the WKB approximation. Due to the inherent deficiencies in calculating nuclear fission probabilities (fission transmission coefficients), it is very difficult to reduce uncertainties in predicting reaction rates both for $\beta$-delayed and neutron-induced fissions in the astrophysical environments. As the first step to overcome the existing deficiencies such as the WKB approximation, we solve the Schroedinger equation for an arbitrary one-dimensional potential energy to calculate the transmission coefficient in the fission channel of compound nucleus reactions, and incorporate the calculated transmission coefficients into the statistical Hauser-Feshbach model. Some calculated results are given to neutron induced reactions on stable actinides, where experimental fission cross section data are abundant. We show that a resonance-like structure appears in the transmission coefficient as well as in the fission cross section when a double-humped fission barrier shape including an intermediate well is adopted. This is understood to be a quantum mechanical effect in the fission channel, since the resonance-like structure is remarkably enhanced when the penetration and reflection waves are in phase.
Speaker: Dr Toshihiko KAWANO (LANL) -
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Experimentally determined 56Ni(n.p) cross section and its impacts on nu-p process
To constrain the nu-p process, we studied the $^{56}$Ni(n,p) reaction by directly measuring the cross section on the radioactive $^{56}$Ni (a half-life of 6 days) at Los Alamos Neutron Science Center. This reaction has been identified as one of critical reactions for understanding the heavy element production in core-collapse supernovae. The radioactive $^{56}$Ni was produced by irradiating protons on a $^{59}$Co foil via the (p,4n) reaction at the Isotope Production Facility and the $^{56}$Ni target was chemically separated, fabricated, and characterized at the Hot Cell facility. Using the LENZ (Low Energy NZ) instrument, the first directly measured cross sections of $^{56,59}$Ni(n,p), $^{56}$Co(n,p), and $^{59}$Ni(n,$\alpha$) will be reported along with experimentally deduced reaction rates of $^{56}$Ni(n,p) and $^{56}$Co(n,p). The impacts of these newly obtained reaction rates and potential further constrains on the nu-p process will be discussed. Ongoing LENZ efforts on (n,p) and (n,$\alpha$) reaction studies with radionuclides such as $^{40}$K, $^{44}$Ti, and $^{26}$Al, and the optimized solenoidal spectrometer development at LANSCE will be presented.
This work benefits from the LANSCE accelerator facility and is supported by the U.S. Department of Energy under contracts DE-AC52-06NA25396, the Laboratory Directed Research and Development program of Los Alamos National Laboratory under project number 20180228ER, and the U.S. Department of Energy Office of Science-Nuclear Physics.
LA-UR-23-25925
Speaker: Hye Young LEE (Los Alamos National Laboratory) -
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Measuring the ${}^{15}\text{O}(\alpha,\gamma)^{19}\text{Ne}$ Reaction Rate in Type I X-ray Bursts using ${}^{20}\text{Mg}$ $\beta$-decay
A neutron star can accrete hydrogen-rich material from a low-mass binary companion star. This can lead to periodic thermonuclear runaways, which manifests as a Type I X-ray bursts detected by space-based telescopes. Sensitivity studies have shown that ${}^{15}\text{O}(\alpha, \gamma){}^{19}\text{Ne}$ carries one of the most important reaction rate uncertainties affecting the modeling of the resulting light curve. This reaction is expected to be dominated by a resonance corresponding to the 4.03 MeV excited state in ${}^{19}\text{Ne}$. This state has a well-known lifetime, so only a finite value for the small alpha-particle branching ratio is needed to determine the reaction rate. Previous measurements have shown that this state is populated in the decay sequence of ${}^{20}\text{Mg}$. ${}^{20}\text{Mg}(\beta p \alpha){}^{15}\text{O}$ events through the key ${}^{15}\text{O}(\alpha, \gamma){}^{19}\text{Ne}$ resonance yield a characteristic signature: the emission of a proton and alpha particle. To identify these coincidence events the GADGET II detection system was used at the Facility for Rare Isotope Beams during Experiment 21072. An ${}^{36}\text{Ar}$ primary beam was impinged on a ${}^{12}\text{C}$ target to create a fast beam of ${}^{20}\text{Mg}$ that fed the ${}^{19}\text{Ne}$ state of interest. We are presenting here the preliminary results from this experiment, which includes discussion of the data processing and analysis methods being used on the newly acquired data, as well as a primer on the development of convolutional neural networks for rare event identification.
Speaker: Tyler WHEELER (Michigan State University)
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Nuclear reaction rates and stellar abundances
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Neutrino process for $^{10}$Be with updated relevant nuclear reactions
We investigated $^{10}$Be production mechanism in the neutrino-process in the core collapsing supernova (CCSN) by including recent updated nuclear reactions relevant to dominant production and destruction of $^{10}$Be. They involve production reactions by neutrinos $^{12}$C and $^{16}$O and other production reactions $^{10}$B(n,p)$^{10}$Be, $^{11}$Be($\gamma$, n)$^{10}$Be. Inverse reactions of the latter two reactions, $^{10}$Be(p,n)$^{10}$B and $^{10}$Be(n, $\gamma$)$^{11}$Be play destruction channels for $^{10}$Be with $^{10}$Be(p,$\alpha$)$^7$Li, $^{10}$Be($\alpha , n$)$^{13}$C. By using recent updated information of relevant reactions and nearby nuclei we tried to pin down the ambiguities from those nuclear reactions. Our results display that other nuclear reactions not discussed yet, such as neutrino reaction on $^{16}$O and $^{11}$Be($\gamma$, n)$^{10}$Be could play vital roles for the $^{10}$Be production int the CCSN.
Speaker: Myung-Ki CHEOUN (Soongsil University) -
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Experimental Study of the $^{30}$Si(p,$\gamma$)$^{31}$P for understanding elemental anomalies in Globular Clusters
Globular clusters are key grounds for models of stellar evolution and early stages of the formation of galaxies. Abundance anomalies observed in the globular cluster NGC 2419, such as the enhancement of potassium and depletion of magnesium [1] can be explained in terms of an earlier generation of stars polluting the presently observed stars [2]. However, the nature and the properties of the polluting stellar sites are still debated. The range of temperatures and densities of the polluting sites depends on the strength of a number of critical thermonuclear reaction rates. The $^{30}$Si(p,$\gamma$)$^{31}$P reaction is one of the few reactions that have been identified to have an influence for elucidating the nature of polluting sites in NGC 2419 [3]. The current uncertainty on the $^{30}$Si(p,$\gamma$)$^{31}$P reaction rate has a strong impact on the range of possible temperatures and densities of the polluter sites.
Hence, we investigated the $^{30}$Si(p,$\gamma$)$^{31}$P reaction with the aim to reduce the uncertainties associated to its reaction rate by determining the strength of resonances of astrophysical interest. In this talk, I will present the study of the reaction $^{30}$Si(p,$\gamma$)$^{31}$P that we performed via the one proton $^{30}$Si($^3$He,d)$^{31}$P transfer reaction at the Maier-Leinbnitz-Laboratorium Tandem, using the high resolution Q3D magnetic spectrograph to measure the angular distributions of the light reaction products. These angular distributions are interpreted in the DWBA (Distorted Wave Born Approximation) framework to determine the proton spectroscopic factor information needed to deduce the proton partial width of the states of interest. This information was used to calculate the $^{30}$Si(p,$\gamma$)$^{31}$P reaction rate. The uncertainties on the reaction rate have been significantly reduced, and key remaining uncertainties have been identified [4]. Complementary direct measurements of $^{30}$Si+p resonance strengths, performed using the DRAGON recoil spectrometer at TRIUMF, will be presented as well. Finally, I will present post-processing calculations showing that the $^{30}$Si(p,$\gamma$)$^{31}$P reaction rates are now sufficiently constrained. Further efforts to unravel the nature of the stellar sites at the origin of the abundance anomalies in globular clusters should now be focused on the other identified key reactions.
[1] C. Iliadis et al., The Astrophysical Journal, 470:140 (2016)
[2] R. G. Gratton et al., The Astronomy and Astrophysics Review 20:50 (2012)
[3] J. R. Dermigny and C. Iliadis, The Astrophysical Journal 848:14 (2017)
[4] D. S. Harrouz et al., Physical Review C 105:015805 (2022)Speaker: Nicolas DE SÉRÉVILLE (IJCLab) -
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Isotopic ratios from (sub)millimetre observations of AGB stars
Asymptotic giant branch (AGB) stars are a late evolutionary phase of low- and intermediate-mass star. They are typified by rapid mass loss through a stellar wind rich in molecular diversity, which is also a key site of dust formation in the universe. Their stellar winds provide a unique opportunity to study the isotopic ratios of various key atomic species that form molecules and whose isotopologues can be easily distinguished in their millimetre and submillimetre spectra. This means that spectrally resolved observations of various isotopologues can tell us about either the properties of the AGB star being studied or the conditions of its natal environment. For example, we can use oxygen isotopic ratios to determine the initial masses of low-mass AGB stars, magnesium isotopic ratios to determine the isotopic ratios of intermediate-mass AGB stars and the isotopic ratios of silicon and sulphur to gauge the initial metallicities of AGB stars. With these direct observations, we can constrain the origins of silion carbide and silicate pre-solar grains. I will discuss my recent results calculating AGB isotopic ratios based on sensitive ALMA observations and future prospects of for this field.
Speaker: Taïssa DANILOVICH (Monash University) -
25
Nucleosynthesis in the tellurium-xenon region
A detailed analysis of nucleosynthesis in the environment of xenon (Z=54) may provide a valuable insight into the interior of stars. The stable isotopes of xenon are produced in a variety of astrophysical environments. The different combinations of nucleosynthetic pathways are: $\gamma$-process for $^{124}$Xe and $^{126}$Xe, $\gamma$- and s-processes for $^{128}$Xe,
s-process for $^{130}$Xe, s- and r-processes for $^{129}$Xe, $^{131}$Xe and $^{132}$Xe, and r-process only for $^{134}$Xe and $^{136}$Xe.
The isotopic composition of Xe observed in different solar system bodies is used as a genetic mark to identify the origin of volatiles on Earth, however, the stellar origin of the many of the observed nucleosynthetic fingerprints is not known.
The xenon isotopic composition has not been observed only in the solar system material. Xenon isotope abundances have been measured also in different types of presolar grains, e.g., in silicon carbide grains and in nano-diamonds, where the contribution of single nucleosynthesis components can be measured.
We present in this work new experimental results relevant for the p-process nucleosynthesis in the Xe region.
Reaction rates of $^{118}$Te(p,$\gamma$), as well as reaction rates for $^{124}$Xe(p,$\gamma$), have been measured in an energy region close to the gamow window.
The performed nucleosynthesis studies include core-collapse supernovae and TP-AGB stars. We study the impact of our preliminary results on the p-process nucleosynthesis of Xe in core-collapse supernovae. In the second part of this work, we discuss the s-process nucleosynthesis in Asymptotic Giant Branch stars for the isotopes of the xenon region.Speaker: Sophia Florence DELLMANN -
26
The Impact of 1D and 3D NLTE Effects on neutron-capture elements
For a long time, 1D LTE (local thermal equilibrium) modelling has been the main approach in spectroscopic abundance determination of elements. However, the recent computational advancements has allowed us to explore both 1D NLTE (non-LTE) and 3D NLTE effects on elemental abundances. In my presentation, I will begin by briefly revisiting the known s-process elements Strontium (Sr) (Bergemann et al., 2012; Gallagher et al., in prep) and Barium (Ba) (Gallagher et al., 2020), as well as discussing the effects of NLTE and 3D on them.
The highlight of this talk will be the introduction of findings from 1D NLTE and 3D NLTE models for Yttrium (Y) (Storm & Bergemann, subm.) and Europium (Eu) (Guo et al. (incl. Storm), in prep). These results, derived using state-of-the-art 3D radiative transfer modeling using code MULTI3D and the most recent nuclear data, will give insight on the implications of NLTE and 3D effects on classification and abundance determination of neutron-capture elements.
Speaker: Nicholas STORM (MPIA)
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22
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Coffee break: Coffee Break & Group Photo
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The early Universe, galactic evolution
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27
Radioactive Decay Lines from the Milky Way - the Pathways of Stellar Ejecta
Soft gamma ray lines from radioactive decay
of 26Al and 60Fe as well as annihilation of positrons have been
observed from the Milky Way. The respective emission contains information
about the ejecta of supernovae, massive-star winds and possibly winds related to neutron stars and
black holes. The distinct spatial structure of the different lines allows
to trace the flow of the ejecta through the interstellar medium.
We have modelled these processes with 3D hydrodynamic simulations.
We find that a large fraction of the massive star ejecta leaves their immediate
surroundings quickly, likely in large superbubble structures, and may even
diffuse into the Galactic halo on the decay timescale of 26Al (~1 Myr).
I will discuss our simulaton results and prospects of the upcoming
NASA mission COSI to trace nucleosynthesis ejecta in the interstellar medium.Speaker: Martin KRAUSE (University of Hertfordshire) -
28
Lithium in the most iron-poor unevolved stars known and the cosmological lithium problem
The most metal-poor low-mass stars formed in the very Early Universe, at about 300 Myr after the Big Bang, are still observable today in the Galactic Halo. These stars hold crucial information of the early epochs of the Universe, such as the properties of the first stars and supernovae and the early chemical evolution of the Universe, and the formation of low-mass stars in the Early Universe.
We identified two very primitive stars, SDSS J0815+4729 and SDSS J0023+0307, using the BOSS survey and follow-up observing campaigns at the 4.2m-WHT and 10.4m-GTC telescopes in La Palma (Aguado et al. 2018a, 2018b; González Hernández et al. 2023). These stars have extremely low iron content (with a [Fe/H] < -5.5) and a unique abundance pattern. The high-quality UVES@8.2m-VLT and HIRES@10m-KeckI spectroscopic data of J0023+0307 (Aguado et al. 2019) and J0815+4729 (González Hernández et al. 2020), respectively, allows us to clearly measure the Li abundance in J0023+0307 at the level of the lithium plateau , whereas in J0815+4729 we are unable to detect Li, thus exacerbating the cosmological lithium problem (González Hernández et al. 2023).
We have also investigated the 6Li/7Li in the most metal-poor spectroscopic binary CS22876-032 using extremely high-resolution (at R~110,000) and high-quality (S/N~580) UVES spectra. CS22876-032, with a metallicity of [Fe/H] ~ -3.7, is about 0.5~dex below the attempts to investigate the 6Li/7Li isotopic ratio in very metal-poor stars from a 3D-NLTE analysis (González Hernández et al. 2019). The lack of evidence of the detection of 6Li has been demonstrated in the re-analysis of some metal-poor stars, using 3D hydrodynamical simulations of metal-poor atmospheres and an appropriate treatment of the Li feature
using 3D-NLTE spectral synthesis (e.g. Steffen et al. 2012; Lind et al. 2013).In this talk I will show a brief summary of the Li and 6Li/7Li abundances at the
lowest metallicities and the implications and prospects to solve the cosmological Li problem.Speaker: Dr Jonay GONZALEZ-HERNANDEZ (Instituto de Astrofisica de Canarias) -
29
Rapidly Rotating Massive Pop III Stars : A Solution for High Carbon Enrichment in CEMP-no Stars
Very metal-poor stars that have [Fe/H]$< -2$ and are enhanced in C relative to Fe ([C/Fe]$>0.7$) but have low enhancement of heavy elements ([Ba/Fe]$<0$) are known as carbon-enhanced metal-poor-no (CEMP-no) stars. These stars are thought to be produced from the interstellar medium (ISM) polluted by the supernova (SN) ejecta of the very first generation (Pop III) massive stars. Although theoretical models of SN explosions from massive Pop III stars can explain the relative abundance pattern reasonably well, the very high enrichment of C $A(\mathrm{C})>6$) observed in many of the CEMP-no stars is difficult to explain when reasonable dilution of the supernova ejecta, that is consistent with detailed simulation of metal mixing in minihaloes, is adopted. We explore rapidly rotating Pop III stars that undergo efficient mixing and reach a quasi-chemically homogeneous (QCH) state. We find that rapidly rotating models that reach the QCH state can eject large amounts of C in the wind and the resulting dilution of the wind ejecta in the interstellar medium can lead to a C enrichment of $A(\mathrm{C})< 7.7$ and can naturally explain the high C enrichment observed in CEMP-no stars. Additionally, the core of QCH stars can produce up to an order of magnitude of higher C than non-rotating progenitors of similar mass and the resulting SN can also lead to high C enrichment of $A(\mathrm{C})< 7$. We find that the abundance pattern from our models that use dilution masses that are consistent with simulations can provide an excellent match to observed abundance patterns in many of the CEMP-no stars. We find that rapidly rotating massive Pop III stars are a promising site for explaining the high C enhancement in the early Galaxy as deduced from CEMP-no stars. This indicates that a substantial fraction of Pop III stars were likely rapid rotators.
Speaker: Jeena S K (Indian Institute of Technology Palakkad) -
30
The 12C/13C isotopic ratio at the dawn of chemical evolution
The 12C/13C isotopic ratio is an important diagnostic tool in astrophysics, providing insights into the formation and evolution of stars and galaxies. In this talk, we will discuss the measurement of this ratio using data from the ESPRESSO instrument, which is one of the most powerful spectrographs in the world.
We will focus on the information obtained from the oldest stars in the Milky Way, the carbon-enhanced metal-poor (CEMP-no) stars. By analyzing the isotopic ratios in these stars, we can determine the changes in the ratio over time and how this has affected the overall composition of the Galaxy. We will also highlight the importance of these measurements for our understanding of the chemical evolution of the Milky Way and the critical role of spectrographs like ESPRESSO in the understanding of our Galaxy.
Speaker: Dr David AGUADO (Instituto de Astrofísica de Canarias)
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27
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Lunch break
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Radioactivity and meteorites
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31
Retrospective r process and supernova signatures in deep-sea archives
Half of the heavy elements are produced in r-process nucleosynthesis, which is exclusively responsible for actinide production, such as Pu-244 (t$_{1/2}$=81 Myr). The r-process requires an explosive scenario but is far from being fully understood; in particular, its sites and history.
The solar system moves through the interstellar medium (ISM) and collects interstellar dust particles that contain such signatures, including the radionuclides Fe-60 (t$_{1/2}$=2.6 Myr) and Pu-244. These nuclides are incorporated into terrestrial archives over millions of years and once recovered can be measured with Accelerator Mass Spectrometry (AMS) with high sensitivity.
Recent technical developments have seen an exceptional gain in measurement efficiency and sensitivity, in particular for actinides, including Pu-244. On the other hand, very large accelerators with >10 million volts allow for effective isobar separation using techniques derived from nuclear physics research. Such AMS systems are unique but required for the identification of small traces of interstellar Fe-60.
New data demonstrate a global Fe-60 influx and is evidence for exposure of Earth to recent (<10 Myr) supernova explosions. In addition, the recent finding in deep-sea archives of ISM-Pu-244, exclusively produced by the r-process, allows to link supernovae and r-process signatures. The low concentrations of Pu-244 measured in deep-sea archives suggest a low abundance of interstellar Pu and supports the hypothesis that the dominant actinide r-process nucleosynthesis is rare. However, the data allow some actinide production in supernovae while implying r-process contributions from additional sources.
Speaker: Prof. Anton WALLNER (HZDR) -
32
Nucleosynthesis from the Galaxy’s current stellar generations
Radioactive parts of nucleosynthesis ejecta transmit the results of nucleosynthesis in stars and supernovae from the current and most recent stellar generations. INTEGRAL observations have measured emission from the long-lived (My) isotopes 26Al and 60Fe over the past 20 years. It is a challenge to decipher these signals in the context of other patchy knowledge and models about these recent stellar populations. Here we report our latest findings about where and how nucleosynthesis ejecta are spread within our Galaxy.
Speaker: Roland DIEHL (MPE Garching, Germany) -
33
Proposed Lunar Measurements of r-Process Radioisotopes to Distinguish the Origin of Deep-sea $^{244}$Pu
The astrophysical sites where r-process elements are synthesized remain mysterious: it is clear that neutron-star-mergers (kilonovae, KNe) contribute, and some classes of core-collapse supernovae (SNe) are also possible sources of at least the lighter r-process species. The discovery of $^{60}$Fe on the Earth and Moon implies that one or more astrophysical explosions have occurred near the Earth within the last few Million years (Myr), probably SNe. Intriguingly, $^{244}$Pu has recently been discovered in deep-sea deposits spanning the past 10 Myr, a period that includes two $^{60}$Fe pulses from nearby supernovae. $^{244}$Pu is among the heaviest r-process products, and we consider whether it was created in the supernovae, which is disfavored by nucleosynthesis simulations, or in an earlier kilonova event that seeded $^{244}$Pu in the nearby interstellar medium that was subsequently swept up by the supernova debris. We discuss how these possibilities can be probed by measuring $^{244}$Pu and other r-process radioisotopes such as $^{129}$I and $^{182}$Hf, both in lunar regolith samples returned to Earth by missions such as Chang'e and Artemis, and in deep-sea deposits.
Speaker: Xilu WANG
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31
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Coffee break
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Novae and X-ray bursts, Type IA supernova and the p-process
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34
Type Ia supernovae: from explosion models to observations
In this biased review talk I will first summarise a modelling workflow (the “pipeline”) that connects rapid binary evolution progenitor models to supernova observables, via supernova explosion and nucleosynthesis simulations. I will then highlight how we can use model specific nucleosynthetic signatures of different explosion models to make inferences about what kind of white dwarfs explode as Type Ia supernovae. This includes population arguments based on the galactic chemical evolution of iron group elements such as manganese, as well as inferences on individual supernovae from the signatures long-lived radioactive isotopes leave in their late-time light curve.
Speaker: Ivo SEITENZAHL (UNSW Canberra) -
35
Recent Advances in the Modeling of Type I X-Ray Bursts and Nova Outbursts
Type I X-ray bursts (XRBs) are thermonuclear explosions in the H/He-rich envelopes accreted onto neutron stars in close binary systems. These events constitute the most frequent type of thermonuclear stellar explosion in our Galaxy (the third, in terms of total energy output after novae and supernovae). To date, most of the efforts undertaken in the modeling of XRBs have relied on non-rotating, 1D hydrodynamic simulations. Here, we present pioneering XRB models computed with different angular velocities (up to 80% of the critical value) and discuss the differences obtained in the lightcurves and in the associated nucleosynthesis with respect to non-rotating models.
It is worth noting that, while all XRB hydro simulations performed to date report that ejection from a neutron star is unlikely, radiation-driven winds during photospheric radius expansion have been suggested to lead to the ejection of a tiny fraction of the accreted envelope. Here, we will report our results of the coupling of a non-relativistic radiative wind model with a series of XRB hydrodynamic simulations, quantifying the expected contribution of XRBs to the Galactic abundances.
Classical novae (CNe) are a related class of thermonuclear explosions that involve mass-accreting white dwarfs, rather than neutron stars. The low-mass, main sequence companion (or a red giant, particularly for recurrent novae) overfills its Roche lobe and matter flows through the inner Lagrangian point of the system. While nova simulations have focused on the early stages of the explosion and ejection, a fraction of the ejecta will collide, first with the accreting disk that orbits the white dwarf, and later with the secondary star. As a result, part of the ejecta is expected to mix with the outermost layers of the secondary. The resulting chemical contamination may have potential implications for the next nova cycle, once mass transfer from the secondary resumes. New multidimensional simulations of the interaction of the ejecta with the accretion disk, and ultimately with the stellar companion, will also be presented.
Speaker: Jordi JOSE (UPC Barcelona) -
36
Understanding the abundance of 22Na in novae by measuring femtosecond lifetimes in 23Mg with a new method
Simulations of explosive nucleosynthesis in novae predict the production of the radioisotope $^{22}$Na. Its half-life of 2.6 yr makes it a very interesting astronomical observable by allowing space and time correlations with the astrophysical object. Its $\gamma$-ray line at 1.275 MeV has not been observed yet by the $\gamma$-ray space observatories. This radioisotope should bring constraints on nova models. It may also help to explain abnormal $^{22}$Ne abundance observed in presolar grains and in cosmic rays. Hence accurate yields of $^{22}$Na are required. At peak nova temperatures, the main destruction reaction $^{22}$Na($p,\gamma$)$^{23}$Mg has been found dominated by a resonance at 0.204 MeV corresponding to the $E_x=$7.785 MeV excited state in $^{23}$Mg. However, the different determinations of the strength of this resonance disagree, resulting in uncertainties of one order of magnitude for the expected mass of $^{22}$Na ejected in novae [1].
An experiment was performed at GANIL facility to measure both the lifetime and the proton branching ratio of the key state at $E_x=$7.785 MeV. The principle of the experiment is based on the one used in [2]. With a beam energy of 4.6 MeV/u, the reaction $^3$He($^{24}$Mg,$\alpha$)$^{23}$Mg$^*$ populated the state of interest. This reaction was measured with particle detectors (magnetic spectrometer VAMOS++, silicon detector SPIDER) and $\gamma$-ray tracking spectrometer AGATA. The expected time resolution with AGATA high space and energy resolutions is 1 fs. Particle and $\gamma$-ray emissions were analyzed with a new simulation code EVASIONS to determine the spectroscopic properties of the key state.
Our new results [3] will be presented. Doppler shifted $\gamma$-ray spectra from $^{23}$Mg states were improved by imposing coincidences with the excitation energies reconstructed with VAMOS++. This ensured to suppress the feeding from higher states. Lifetimes in $^{23}$Mg, down to the femtosecond, were measured with a new approach based on particle - $\gamma$-ray correlations and velocity-difference profiles. Protons emitted from unbound states in $^{23}$Mg were also identified. With an higher precision on the measured lifetime and proton branching ratio of the key state, a new value of the resonance strength $\omega\gamma$ was obtained, it is below the sensitivity limit of direct measurement experiments. The $^{22}$Na($p,\gamma$)$^{23}$Mg thermonuclear rate has been reevaluated with the statistical Monte Carlo approach. The amount of $^{22}$Na ejected during novae has been proven to be a tool for better understanding the underlying novae properties. Thanks to the highly-accurate rate, derived here, robust estimates of the detectability limit of $^{22}$Na in novae have been determined with respect to the next generation of $\gamma$-ray space telescopes, and the detection of the $^{22}$Na $\gamma$-ray line found promising in the coming decades.
References
[1] C. Fougères et al, EPJ Web Conf 279, 09001 (2023).
[2] O. S. Kirsebom et al, Phys. Rev. C 93, 1025802 (2016).
[3] C. Fougères et al, arXiv:2212.06302, 09001 (2022).Speakers: Chloé FOUGÈRES (Argonne National Laboratory), Dr François DE OLIVEIRA SANTOS (Grand Accélérateur National d'Ions Lourds (GANIL, CEA/DRF-CNRS/IN2P3) -
37
Simulations of One and Two Star Explosions in the Double Degenerate Double Detonation Scenario for Type Ia Supernovae
The precise origin of Type Ia supernovae (SNe Ia) is unknown despite their value to numerous areas in astronomy. While it is a long-standing consensus that they arise from an explosion of a C/O white dwarf, the exact progenitor configurations and explosion mechanisms that lead to a SN Ia are still debated. One popular theory is the double detonation in which a helium layer, accreted from a binary companion, detonates on the surface of the primary star, leading to a converging shock-induced detonation of the underlying core. Across a mass range of sub-Chandrasekhar progenitors, the double detonation scenario produces light curves and spectra that match many characteristics of individual SNe Ia as well as the breadth of the population. It has also recently been shown via simulation that the elusive donor companion may not survive but rather undergo its own double detonation triggered by the impact from the core detonation of the primary star. If this explosion of the companion does indeed occur in reality, it could have numerous implications for the observables and nucleosynthesis from SNe Ia. In this talk, we show 2D simulations of detonations in white dwarf binaries that model both stars undergoing a double detonation in addition to double detonations in isolated, thin helium shell progenitors. We also present radiative transfer results from these two scenarios, which includes the first multi-dimensional synthetic observables of the two star double detonation. We find that within a range of mass configurations of the degenerate binary, the synthetic light curves and spectra of these events match observations as well as theoretical models of single double detonations do. Notably, one and two star double detonations that are spectrally similar and reach the same peak brightnesses produce different amounts of Si- and Fe-group elements which would affect the impact of SNe Ia on the chemical evolution of the universe. Further understanding of this scenario is needed in order to determine if at least some observed SNe Ia actually originate from two stars exploding.
Speaker: Samuel BOOS (University of Alabama)
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34
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Poster session (Core-collapse supernovae, mergers and the r-process)
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38
Superheavy Elements in Kilonovae
With LIGO-Virgo-KAGRA in its fourth observing run, a new opportunity to search for electromagnetic counterparts of compact object mergers is also upon us. The light curves and spectra from the first "kilonova" associated with a binary neutron star binary (NSM) suggests that these sites are hosts of the rapid neutron capture ("r") process. However, it is unknown just how robust elemental production can be in mergers. Identifying signposts of the production of particular nuclei is critical for fully understanding merger-driven heavy-element synthesis. This talk will explore the properties of very neutron rich nuclei for which superheavy elements ($Z\geq 104$) can be produced in NSMs and whether they can similarly imprint a unique signature on kilonova light-curve evolution. A superheavy-element signature in kilonovae represents a route to establishing a lower limit on heavy-element production in NSMs as well as possibly being the first evidence of superheavy element synthesis in nature.
Speaker: Erika HOLMBECK (Observatories of the Carnegie Institution for Science) -
39
Strong magnetic field impact on the neutrino process inside the SNe explosion
Strong magnetic fields such as MHD-Jet SNe could exist in the inner region of the explosive astrophysical site. The phase space of the electrons is quantized inside the magnetic field so that the weak interaction rates deviate from the field-free case. This talk focuses on the (anti)neutrinos absorption process. This process is essential since it determines the opacity of the neutrino and the position of the (anti) neutrino sphere. Moreover, we will show that the evolution of the electron fraction 𝑌𝑒 is also affected by the magnetic field since its value depends on the inverse reaction of the neutrino process. Such impact could leave an imprint on the 𝑟-process nucleosynthesis yields.
Speaker: Yudong LUO (Peking University) -
40
Multi-messenger Signals of Heavy Axionlike Particles in Core-collapse Supernovae
Axion-like particles (ALPs) are a class of hypothetical pseudoscalar particles which feebly interact with ordinary matter. The hot plasma in core-collapse supernovae is a possible laboratory to explore physics beyond the standard model including ALPs. Once produced in a supernova, a part of the ALPs can be absorbed by the supernova matter and affect energy transfer. We recently developed two-dimensional supernova models including the effects of the production and the absorption of ALPs that couple with photons. It is found that the additional heating induced by ALPs can enhance the explosion energy; for moderate ALP-photon coupling, we find explosion energies ~0.610^51 erg compared to our reference model without ALPs of ~0.410^51 erg. Our findings also indicate that when the coupling constant is sufficiently high, the neutrino luminosities and mean energies are decreased because of the additional cooling of the proto-neutron star. The gravitational wave strain is also reduced because the mass accretion on the proto-neutron star is suppressed.
Speaker: Kanji MORI (National Astronomical Observatory of Japan) -
41
Atomic Structure Calculations of Neodymium and Uranium for Kilonova Emission Modeling
In 2017, the electromagnetic counterpart AT2017gfo to the binary neutron star merger GW170817 was observed by all major telescopes on Earth. While it was immediately clear that the transient following the merger event, is powered by the radioactive decay of r-process nuclei, only few tentative identifications of light r-process elements have been made so far. One of the major limitations for the identification of heavy nuclei based on light curves or spectral features is incomplete or missing atomic data which greatly affects the results of radiative transfer models. While progress has been made on lanthanide atomic data over the last few years, for actinides there has been less emphasis, with the firs set of opacity data only recently published.
This talk will present converged large-scale atomic structure calculations of lanthandies (focusing on neodymium, $(Z=60)$) as well as actinides (focussing on uranium, $(Z=92)$). Using two different codes (FAC and HFR) for the calculation of the atomic data, we investigate the accuracy of the calculated data (energy levels and electric dipole transitions) and their effect on kilonova opacities. I will show a comparison of bound-bound opacities as a function of included electron configurations, for both ab-initio and experimentally calibrated atomic structure calculations. Finally, I will present how optimization of the local central potential model in atomic structure calculations increases the accuracy of the obtained level energies, and, as a result, the opacities.
Speaker: Dr Andreas FLÖRS (GSI Darmstadt) -
42
MeV Gamma Rays from Neutron Star Mergers: a Distinct Signature of r-Process Fission
Neutron star mergers (NSMs) are the first verified sites of rapid neutron capture (r-process) nucleosynthesis, and could emit gamma rays from the radioactive isotopes synthesized in the neutron-rich ejecta. These MeV gamma rays may provide a unique and direct probe of the NSM environment as well as insight into the nature of the r process, just as observed gammas from the 56Ni radioactive decay chain provide a window into supernova nucleosynthesis. Here we include the photons from fission processes for the first time in estimates of the MeV gamma-ray signal expected from an NSM event. We consider NSM ejecta compositions with a range of neutron richness and find a dramatic difference in the predicted signal depending on whether or not fissioning nuclei are produced. The difference is most striking at photon energies above ∼3.5 MeV and at a relatively late time, several days after the merger event, when the ejecta is optically thin. We estimate that a nearby NSM could be detectable by a next generation MeV gamma-ray detector, up to ∼10$^4$ days after the merger, if fissioning nuclei are robustly produced in the event. In addition, such MeV signal from NSM, if detected, can constrain the nuclear models for the heavy r-process nuclei that without experimental data.
Speaker: Xilu WANG -
43
New Observable Signal of r-, i-, and s-process Nucleosynthesis in Collapsar Jet
In the era of multi-messenger astronomy, the afterglow of energetic photons emitted from the decay of long-lived neutron-rich actinides is an important observable signal for the rapid neutron-capture process (r-process) which occurred in the compact gravitational objects, i.e., binary neutron star merger (NSM), magneto-hydrodynamic jet supernova (MHDJ SN), and collapsar, which is an explosion of single massive star collapsing to a black hole. We calculated the collapsar nucleosynthesis including the fission of wide ranges of heavy nuclei for a long time (up to 10^17 seconds). We have recently found [1], for the first time, that the intermediate and slow neutron-capture processes (i- and s-processes) operate at a relatively later time in collapsar nucleosynthesis as secondary processes, when the primary r-process nuclei capture the neutrons produced by the fission of long-lived neutron-rich actinides. Here we show that the collapsar provides with another significant observable signal in the nucleosynthesis of heavy atomic nuclei.
In this article, we show the roles of neutron-capture reactions on unstable nuclei near the stability line in the i-process as well as those on extremely neutron-rich nuclei in the r-process. We also propose that the pronounced odd-even pattern in the mass-abundance relation near rare earth elements in metal-deficient halo stars could be a piece of observational evidence of the collapsar s- and -processes [1]. The s- and i-processes are believed to occur in asymptotic giant branch (AGB) stars to provide half of heavy atomic nuclei 90 ≤ A in the Milky Way. Collapsar nucleosynthesis is one of the dominant sites for the production of heavy r-process nuclei over the entire history of Galactic chemical evolution until solar system formation [2]. Therefore, our finding [1] would motivate to improve an accepted standard interpretation that the solar r-abundance is the residual of the measured solar-system abundance subtracted by the s-abundance.[1] Z. He, M. Kusakabe, T. Kajino, S.-G. Zhou, H. Koura, S. Chiba, submitted (2022).
[2] Y. Yamazaki, Z. He, T. Kajino, G. J. Mathews, M. A. Famiano, X.-D. Tang, J.-R. Shi, ApJ. 933 (2022), 112.Speaker: Zhenyu HE (Beihang University) -
44
Constraining Supernova Nucleosynthesis from nu-Mass Hierarchy and the Roles of nu-Nucleus and Radioactive Nuclear Reactions
The origin of neutrino mass and mass hierarchy is one of the biggest unanswered questions in physics. In this article, we propose an astrophysical method so that the supernova (SN) $\nu$-process nucleosynthesis, which is consistent with the mass hierarchy constrained from various $\nu$-oscillation experiments, should provide independent observational signals of nucleosynthetic products in the specific nuclei such as $^{138}$La, $^{98}$Tc, $^7$Li, $^{11}$B and others (so-called $\nu$-nuclei) through the $\nu$-flavor oscillation due to the MSW matter effect and the effect of collective oscillation [1].
Core-collapse SNe emits a huge number of neutrinos which bring valuable observational information on how the neutrinos propagate through the high-density matter and change their flavors and how explosive nucleosynthesis occurs. We found that the still unknown mass hierarchy is imprinted in the nucleosynthetic products of $\nu$-nuclei [1,2]. In this talk, we will discuss the mechanism of SN $\nu$-process nucleosynthesis and try to constrain the mass hierarchy by comparing our theoretical prediction of nuclear abundances and observed values in the meteorites. Among the calculated results, the abundance ratios of $^7$Li/$^{11}$B and $^{138}$La/$^{98}$Tc provide exclusively sensitive probes to neutrino mass hierarchy [1]. These ratios are also influenced by the mass cut during the ejection phase of SN materials. These facts provide valuable quantitative tools to constrain the mass hierarchy through precise measurements of nuclear abundances of these $\nu$-nuclei in SiC-X pre-solar grains and comprehensive studies of solar-system abundances. We also found the significance of removing the uncertainties associated with the $\nu$-$^4$He,$^{12}$C,$^{16}$O, and $^{20}$Ne reaction cross sections with all possible final particle-emission channels being taken into account and the radioactive nuclear reaction rates for $^{11}$C($\alpha,p)^{14}$N and many others for the production of these $\nu$-nuclei. We will discuss these sensitivities and propose a list of $\nu$-A and radioactive nuclear reactions to be studied experimentally and theoretically [3].[1] Xingqun Yao, T. Kajino, M. Kusakabe et al., Paper-I (2023), to be submitted.
[2] Heamin Ko, D. Jang, M.-K. Cheoun, M. Kusakabe, H. Sasaki, X. Yao et al., ApJ 937 (2022), 2, id.116, 37pp.
[3] Xingqun Yao, T. Kajino, M. Kusakabe et al., Paper-II (2023), to be submitted.Speaker: Xingqun YAO (Beihang Univ. & National Astronomical Observatory of Japan) -
45
Follow-up of bright very metal-poor star candidates discovered by narrow-band survey
Chemical abundance of metal-poor stars is a clue to understand the chemical evolution of the early Universe. However, the metal-poor stars discovered by previous surveys are faint and it is difficult to measure their abundance of many elements with high precision. Therefore, we performed a photometric survey using the wide-field CMOS camera (Tomo-e Gozen Camera) on the Kiso Schmidt telescope with narrow-band filters sensitive to stellar metallicity to search for bright metal-poor stars. Very metal-poor star candidates with [Fe/H] < -2 were selected for follow-up medium-resolution spectroscopy with the Nayuta telescope. We establish a method for analyzing medium-dispersion spectra using 43 stars with metallicity measurements and determine the metallicity and abundance of alpha-elements of ~300 metal-poor star candidates that we have followed up so far. As a result, nine new very metal-poor stars and two low-alpha stars were discovered. In this talk, we present the results of the follow-up and the metal-poor star candidate selection methods.
Speaker: Hiroko OKADA (University of Hyogo) -
46
Probing the origin of heavy isotopes in dwarf galaxies with a variable initial mass function
Astrophysical sources of r-process nucleosynthesis pose an ongoing enigma, with conflicting findings in the literature. We investigate three leading candidates—neutron star mergers, magneto-hydrodynamic jets, and collapsars—each associated with distinct stellar progenitor mass ranges. However, an overlooked bias in r-process studies arises from the influence of the initial mass function (IMF), which has been recently confirmed to vary with metallicity. This IMF variation affects the proportion of stars formed within specific mass ranges relative to metallicity, consequently impacting the rate of enrichment for potential r-process sites.
To address the influence of a variable IMF on r-process enrichment, we extend our open-source galactic chemical evolution model, GalCEM. GalCEM enables comprehensive calculations of the chemical evolution of all stable isotopes across galactic times. The code encompasses in synergy low-to-intermediate stars, massive stars, type Ia supernovae, and the aforementioned candidate processes. Our novel extension employs the integrated galaxy-wide IMF (IGIMF), a well-established and observationally validated theory. The IGIMF demonstrates remarkable consistency across diverse environments, including the Milky Way, high-redshift starburst galaxies, and local dwarf galaxies. We focus specifically on local dwarf galaxies and their low-metallicity stars, as they serve as self-contained nucleosynthetic laboratories, devoid of complex dynamic evolution.
Our study unveils the return rates of r-process nucleosynthesis candidates within the context of a variable IMF. This works provides fundamental constraints for future observational studies.
Speaker: Eda GJERGO (Nanjing University) -
47
High-dispersion spectroscopic observations of r-process elements including thorium in solar metallicity and mildly-metal-poor stars
The origin of the r-process is unknown for many years, but in 2017, neutron-star merger (NSM) was observed by gravitational waves [1], it was found that NSM is the origin of the r-process by following photometric and spectroscopic observation. However, NSM is unable to explain the origin of the r-process alone. Observations of stellar abundances have found stars which have high [Th/Eu] value (Actinide-Boost stars). The origin of Actinide-Boost stars is unclear, the existence of such stars suggests that the r-process has more than one origin (e.g. [2, 3]). It is important to determine Th abundance in many stars to clarify the origin of the r-process. At present, there has been few observations of Th in [Fe/H] > -1.5 [4]. Therefore, we obtained a number of r-process abundances including Th, over ten objects in [Fe/H] > -1.5. We observed with Nayuta/MALLS and obtained Subaru/HDS archive data. We found the following two results. First, the value of [Th/Eu] is constant and independent of the metallicity. Second, there are not Actinide-boost stars in [Fe/H] > -1.5. These results are important to clarify the origin of Actinide-boost stars. Identifying the origins of Actinide-boost stars is to investigate the origins of the r-process.
[1] Abbott et al., PhRvL, 119, 16 (2017)
[2] Holmbeck et al., ApJ, 859, 2 (2018)
[3] Yong et al., Nature, 595, 7866 (2021)
[4] Mishenina et al., MNRAS, 516, 3 (2022)Speaker: Kurumi FURUTSUKA (University of Hyogo) -
48
Bright metal-poor star survey with Tomo-e Gozen Camera
The first metal enrichment in the Universe was made by a supernova explosion of a population III star. Second-generation stars were formed from the mixture of the pristine gas and the supernova ejecta. Metal-poor stars were survivors of second-generation stars in the Galactic halo. Their abundance pattern records the metal abundance at their formation and tell us the chemical evolution in the early Universe. Therefore, large programs to survey metal-poor stars are performed and provide metal-poor star candidates and high-resolution spectroscopic follow-ups measure the metallicities and abundances of the metal-poor stars. These intensive observations constrain the chemical evolution and the nature of supernovae in the early Universe. To enhance this study, the discovery of bright metal-poor stars, for which the high-resolution spectroscopic follow-up is easy, is desired. Therefore, we plan to search for all bright metal-poor stars in the northern hemisphere using narrow-band CaHK filters and the Tomo-e Gozen Camera on the Kiso Schmidt Telescope at the University of Tokyo. We report the status of a pilot survey having been performed over 5000deg2 in 2022 and the survey plan.
Speaker: Nozomu TOMINAGA (NAOJ) -
49
Kilonova Modelling: Nuclear Physics, Magnetic Fields, Neutrinos
The merging of two neutron stars can provide the conditions necessary for the production of the heaviest elements in the universe via the rapid neutron capture process (r-process). When this occurs, an abundance of material is produced lying far from nuclear stability, and the decays of these nuclei produce the electromagnetic signal: the kilonova. Modeling these kilonova signals remains subject to uncertainties stemming from both nuclear properties far from stability as well as from incomplete information regarding the evolution of the extreme astrophysical environment in which this occurs.
I will discuss current work aimed at approaching this problem from both an astrophysical perspective with magnetohydrodynamic simulations of the post-merger disk with neutrino transport, as well as from a nuclear perspective with detailed nucleosynthesis studies. I will highlight recent results in identifying key nuclei for the nuclear heating that powers the kilonova as well as the effect of nuclear uncertainties on cosmochronometry calculations for r-process enhanced metal-poor stars.
Speaker: Kelsey LUND (North Carolina State University) -
50
Supernova gravitational waves and asteroseismology
The supernova, which is the event at the last moment of the massive star's life, is the next promising candidate as the gravitational wave source. Up to now, gravitational waves from supernova explosions have been mainly discussed via numerical simulation. These results tell us the existence of the gravitational waves whose frequencies increase from a few hundred hertz up to kHz within a second. However, the physics behind this signal has been unclear. In this talk, we discuss the supernova gravitational waves from the approach with asteroseismology and we show the universal relation in the supernova gravitational waves. Using our relation, once one detects the gravitational waves from the supernova, one can estimate the evolution of the average density of the protoneutron star.
Speaker: Dr Hajime SOTANI (RIKEN) -
51
Systematic 3D simulations of core-collapse supernova and implications for explosive nucleosynthesis
Systematic studies of core-collapse supernovae (CCSNe) have been conducted based on hundreds of one-dimensional artificial models (O'Connor & Ott 2011,2013; Ugliano et al. 2013, Ertl et al. 2015) and two-dimensional self-consistent simulations (Nakamura et al. 2015;2019, Burrows & Vartanyan 2020). We have performed three-dimensional core-collapse simulations for 16 progenitor models covering ZAMS mass between 9 and 24 solar masses. Our CCSN models show a wide variety of shock evolution, explosion energy, and properties of the ejected material. Most of our models have proton-rich ejecta as usual in neutrino-driven explosions, but some of them involve neutron-rich (Ye<0.45) material. We will discuss the impacts of such a divergence of the ejecta properties on explosive nucleosynthesis.
Speaker: Ko NAKAMURA -
52
Sensitivity of r-abundance to the intermediate mass nuclear reactions
We investigate the sensitivity of the r-process nucleosynthesis to intermediate-mass nuclear reactions. Many nuclear reactions with neutron-rich nuclei are still uncertain and the r-process sites are not fully understood. We use Meyer's code for the reaction network calculation and update some reaction rates. Then, we calculate the r-process nucleosynthesis in the core-collapsed supernovae for the magnetohydrodynamic (MHD) jet model. The sensitivity of the r-abundance to these reactions is estimated when there is an artificial increase in the thermonuclear reaction rates. We discuss reaction network flows under the various conditions and features of affection of intermediate-mass nuclear reactions to the r-process nucleosynthesis.
Speaker: Dr Kyungil KIM (Institute of Rare Isotope Science, Institute for Basic Science) -
53
Influence of key SN properties on Galactic Chemical Evolution
Galactic chemical evolution (“GCE”) is a great tool to probe the influence of various astrophysical sites on the observed abundances of stars. We use the high resolution ((20 pc)^3 /cell) inhomogeneous GCE tool “ICE” to estimate the impact of two main supernova (“SN”) properties on observed stellar abundances:
First, we will show that supernova yields need to be metallicity dependent in order to explain the observed alpha element abundances.
Second, we show that SN explosion energies have a significant impact on the mixing of the interstellar medium.
We further use pedicted SN explosion energies to constrain under which circumstances SNe “fail”, i.e., collapse to a black hole instead of leaving behind a neutron star. We then use these predictions to estimate if black hole – neutron star mergers might be a second, earlier acting rapid neutron capture (“r”) process production site.
Finally, we speculate whether a rare sub class of supernovae (“magnetorotationally driven supernovae”) can act as an additional and earlier r-process site and conclude that our simulations with an adequate combination of these two sites successfully reproduce the observed r-process elemental abundances in the Galactic halo.
Speaker: Benjamin WEHMEYER (Konkoly Obs & Univ Hertfordshire) -
54
Galactic chemical Evolution with short lived radioactive isotopes
Studying the galactic chemical evolution with short lived radioisotopes (SLRs) has a significant advantage over using stable elements: Due to their radioactive decay, SLRs carry additional timing information on astrophysical nucleosynthesis sites.
We can use meteoritic abundance data in conjunction with a chemical evolution model to constrain the physical conditions in the last rapid neutron capture process event that polluted the early Solar system prior to its formation [1].
Further, with the help of detections of live SLRs of cosmic origin in the deep sea crust [2], we can use these data in a 3-dimensional chemical evolution code to explain why different classes of radioisotopes should often arrive conjointly on Earth, even if they were produced in different sites (e.g., neutron star mergers, core-collapse/thermonuclear supernovae) [3].
Finally, we included radioisotope production into a cosmological zoom-in simulation to create a map of Al-26 decay gamma-rays indicating areas of ongoing star formation in the Galaxy, consistent with the observations by the SPI/INTEGRAL instrument [4]. We provide predictions for future gamma-ray detection instruments.
[1] Côté et al., 2021 Science 371, 945
[2] Wallner et al., 2021 Science 372, 742W
[3] Wehmeyer et al., 2023 ApJ 944, 121
[4] Kretschmer et al., 2013 A&A 559, A99Speaker: Benjamin WEHMEYER (Konkoly Obs & Univ Hertfordshire) -
55
Insight to the Explosion Mechanism of Core Collapse Supernovae Through $\gamma$-ray Spectroscopy of $^{46}$Cr
Currently, the explanation behind the explosion mechanism of core collapse supernovae is yet to be fully understood. New insight to this phenomena may come through observations of $^{44}$Ti cosmic $\gamma$ rays; this technique compares the observed flux of cosmic $^{44}$Ti $\gamma$ rays to that predicted by state-of-the-art models of supernova explosions. In doing so, the mass cut point of the star can be found, a key hydrodynamic property of supernova that provides an understanding of the material that is either ejected from the explosion or bound to the residual neutron star or black hole. However, a road block in this procedure comes from a lack of precision in the nuclear reactions that destroy $^{44}$Ti in supernovae, most notably the reactions $^{44}$Ti$(\alpha,p)^{47}$V and $^{45}$V$(p,\gamma)^{46}$Cr. Therefore, this study aims to better understand the $^{45}$V$(p,\gamma)^{46}$Cr reaction by performing $\gamma$-ray spectroscopy of $^{46}$Cr with the aim of identifying proton-unbound resonant states.
The experiment was conducted at the ATLAS facility at Argonne National Laboratory, using the GRETINA+FMA setup. A beam of 120-MeV $^{36}$Ar ions are impinged onto a ~200 $\mu$g$\cdot$cm$^{-2}$ thick $^{12}$C target, producing $^{46}$Cr via the fusion-evaporation reaction $^{12}$C($^{36}$Ar,2$n$). The cross section for producing $^{46}$Cr, in this reaction, is estimated to be in the $\mu$b range. Nevertheless, with the power of the GRETINA+FMA setup, we show that it is possible to cleanly identify $\gamma$ rays in $^{46}$Cr. These include decays from previously unidentified states above the proton-emission threshold, corresponding to resonances in the $^{45}$V + $p$ system. This represents the state-of-the-art for in-beam $\gamma$ ray studies for full spectroscopy up to the excitation energy region relevant for astrophysical burning.
Speaker: Christopher COUSINS (University of Surrey)
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38
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Poster session (High-density matter)
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56
Density dependence of the nuclear symmetry energy: dilute and dense matter
The properties of neutron-rich nuclear systems are largely determined by the density dependence of the nuclear symmetry energy. Experiments aiming to measure the neutron skin thickness [1,2] and astronomical observations of neutron stars and gravitational waves [3,4] offer valuable information on the symmetry energy at sub- and supra-saturation densities, respectively.
The Korea-IBS-Daegu-SKKU (KIDS) theoretical framework for the nuclear eqution of state (EoS) and energy density functional (EDF) [5-7] offers the possibility to explore the symmetry-energy parameters such as $J$ (value at saturation density), $L$ (slope at saturation), $K_{\mathrm sym}$ (curvature at saturation), and so on, independently of each other and independently of assumptions about the in-medium effective mass. Within this versatile and physically motivated framework, any set of EoS parameters can be transposed into a corresponding EDF and readily tested in microscopic calculations of nuclear properties [6-8]. Related studies within KIDS of symmetry-energy parameters based on both astronomical observations and bulk nuclear properties [8,9] and a comprehensive Bayesian analysis of both isoscalar and isovector nuclear observables including giant resonances [10] were published recently.
In this talk, I plan to discuss the importance of high-order parameters such as $K_{\mathrm sym}$, indications for a model decoupling of the nucleonic fluid from dense and dilute regimes, implications for the PREX-CREX puzzle, and first attempts to extend the framework to quarkionic matter [11].
References
[1] T. Aumann et al., Phys. Rev. Lett. 119 (2017) 262501.
[2] D. Adhikari et al. (PREX Collaboration), Phys. Rev. Lett. 126 (2021) 172502;
D.Adhikari et al. (CREX Collaboration), Phys. Rev. Lett. 129 (2022) 042501.
[3] B. P. Abbott et al., Phys. Rev. X 9 (2019) 011001.
[4] M. C. Miller et al., Ap.J.L. 918 (2021) L28.
[5] P. Papakonstantinou et al., Phys. Rev. C 97 (2018) 014312.
[6] H. Gil, P. Papakonstantinou, C. H. Hyun, Y. Oh, Phys. Rev. C 99 (2019) 064319.
[7] H. Gil et al., Phys. Rev. C 100 (2019) 014312.
[8] H. Gil et al., Phys. Rev. C 103 (2021) 034330.
[9] H. Gil, P. Papakonstantinou, C. H. Hyun, Int. J. Mod. Phys. E 31 (2022) 2250013.
[10] Jun Xu, P. Papakonstantinou, Phys. Rev. C 105 (2022) 044305.
[11] P. Papakonstantinou, C. H. Hyun, Summetry 15 (2023) 683.Speaker: Panagiota PAPAKONSTANTINOU (IBS / RISP) -
57
Non-equilibrium dynamics in the inner crust of a neutron star
We analyze the behavior of a nucleus as it moves through a superfluid neutron medium located in the inner crust of a neutron star. One important aspect of studying the behavior of nuclei in neutron stars immersed in superfluid neutrons is understanding how their effective mass is affected by interactions with the surrounding particles. To study it, we utilized the Time-Dependent Hartree-Fock-Bogoliubov framework, which allowed us to systematically extract an effective mass for different densities in the low-velocity limit. We use one of the latest nuclear energy-density functionals from the Brussels-Montreal family, developed specifically for applications to neutron superfluidity in neutron-star crusts.
Through investigating our system with no geometry restrictions, we identified several dissipation mechanisms: the production of phonons, the breaking of Cooper pairs, and the creation of vortex rings. The last channel is present only in some layers, which might have consequences for the details of glitch creation.
Speaker: Dr Daniel PĘCAK (Warsaw University of Technology) -
58
Beta-Decay of Mg-33 for Urca Cooling in Accreting Neutron Star Crusts
Low Mass X-ray Binaries that transiently accrete matter onto their neutron stars are excellent laboratories for studying dense matter physics. These systems go in and out of the quiescence phase over observational timescales of decades. Monitoring the surface temperatures of neutron stars in this phase reveals a great deal of information about their structure and composition. However, to infer these properties, it is necessary to have a complete understanding of different nuclear reactions that heat or cool the crust. Urca cooling is one such source of neutrino cooling in the crust that strongly depends on the ground-state to ground-state $\beta$-decay transition strengths. $A = 33$ mass chain, and specifically the $^{33}$Mg - $^{33}$Al transition is the strongest Urca cooling agent for crusts composed of X-ray burst ashes. This relies partly on the strong ground state branch measured in high resolution $\beta$-delayed $\gamma$-spectroscopy of $^{33}$Mg. However, recent measurements of a negative parity ground state in $^{33}$Mg makes this a first forbidden decay and the strong transition strength is questioned in the literature, citing Pandemonium effect as a possible reason. We try to resolve this anomaly using Total Absorption Spectroscopy that is mostly free of this Pandemonium effect. I will present the $\beta$-decay of $^{33}$Mg experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) with NERO/BCS/SuN detector system and discuss results from ongoing analysis. This measurement will also provide more information about the nuclear structure effects near the $N = 20$ island of inversion and how they manifest in astrophysical systems.
Speaker: Rahul JAIN (MSU/FRIB) -
59
Probing hadron-quark phase transition in inspiralling neutron stars
The discovery of GW170817 has significantly advanced our understanding of the high-density equation of state. In this talk, I will showcase our recent findings, which involve constraining the hadron-quark phase transition using both the existing GW170817 data and future GW observations. The discussion will encompass the constraints derived from both quasi-equilibrium tides and dynamic tides.
Speaker: Zhiqiang MIAO (Xiamen University) -
60
Neutrino and Anti-neutrino Emission from Neutron-Star Matter with Strong Magnetic Field in a Relativistic Quantum Approaches
Neutrino and antineutrino emissions are dominant for the cooling process of neutron-stars (NSs). Since neutrino emission rates depend on physical circumstances inside NSs, the study of NS cooling through neutrino emission gives important information for constraining internal NS structures. On the other hand, magnetic fields in NSs play important roles in the interpretation of many observed phenomena. In particular, magnetars, which are associated with super strong magnetic fields, have properties different from normal neutron stars (NSs). Thus, phenomena related magnetars can provide a lot of information about the physics of the strong magnetic field.
There are several kinds of the cooling processes such as the direct Urca (DU) process, the modified Urca process and the neutrino and anti-neutrino pair emission process through the Bremsstrahlung in NN scattering (NN-pair). In these processes the neutrino emission rates must be affected by the magnetic-field because these processes are restricted by the energy-momentum conservation, and a magnetic field provides additional momentum to the particles.
In this work, we study the NN-pair emission [1] and direct Urca [2] process under strong magnetic field in a relativistic quantum approach. We solve exact wave functions for protons and electrons in the states described with Landau levels and calculate neutrino (anti- neutrino) emissions from the transition between two different Landau levels, so that the NN-pair emission can be treated by one-body process.
Then we obtain the following results.
In $10^{15}$ G of the magnetic field, the energy loss of the NN-pair process is much larger than that of the modified Urca process. In addition, the neutrino emission increases as the magnetic field is weaker around $10^{14}-10^{15}$ G. Therefore, the neutrino emissivity of the NN pair process must be very effective in relatively low density region. Even the direct Urca process can satisfy the kinematic constraints even in the density regions where this process could not normally occur in the absence of a magnetic field.
Thus, the strong magnetic field plays a very important role to increase the neutrino emissivity in NSs with strong magnetic fields.[1] T.Maruyama et al., Phys. Lett. B 805, 135413 (2020)
[2] T.Maruyama et al., Phys. Lett. B 824, 136813 (2022)Speaker: Tomoyuki MARUYAMA (Nihon university) -
61
Investigating the possible existence of hyper-heavy nuclei in a neutron-star environment
The synthesis of hyper-heavy elements is investigated under conditions simulating neutron star environment. The constrained molecular dynamics approach is used to simulate low energy collisions of extremely n-rich
nuclei. A new type of the fusion barrier due to a neutron wind is observed when the effect of neutron star environment (screening of Coulomb interaction) is introduced implicitly. When introducing also a background of surrounding nuclei, the nuclear fusion becomes possible down to temperatures of 10$^8$ K and synthesis of extremely heavy and n-rich nuclei appears feasible. A possible existence of hyper-heavy nuclei in a neutron star environment could provide a mechanism of extra coherent neutrino scattering or an additional mechanism, resulting in x-ray burst or a gravitational wave signal and, thus, becoming another crucial process adding new information to the suggested models on neutron star evolution.Speaker: Dr Vlasios PETOUSIS (Institute of Experimental and Applied Physics - Czech Technical University, 11000 Prague, Czechia) -
62
Do Accreting Neutron Stars All Have Identical Crusts?
Accretion onto a neutron star induces nuclear reactions which heat the crust. By fitting crust models to the observed thermal evolution of the neutron star after accretion halts and the neutron star enters quiescence, we obtain constraints on the composition and heating of the neutron star crust, notably the crust impurity concentration and the amount of heat deposited per accreted nucleon. Heat deposition in the shallowest layers of the crust is required to fit the early-time cooling as well as to explain the observed recurrence time of superbursts, but the physical mechanism that causes this heating is unknown. It is also unknown whether this shallow heating is constant among different accretion outbursts and different neutron stars and whether different neutron stars have the same crust composition.
We model the thermal evolution of seven neutron stars in which crustal cooling has been observed using the crust cooling code dStar. We estimate the model parameters by performing Markov Chain Monte Carlo fits to the observational data. To test whether model parameters are constant across different outbursts and neutron stars, we perform our analysis first for each neutron star independently, then perform joint fits in which the heat deposition or crust impurity are shared among all neutron stars. We find that models in which the shallow heating is shared across neutron stars fit the data significantly more poorly than those in which it is not shared. This suggests that the shallow heating is indeed different for different neutron stars.
Speaker: Justin GRACE (Michigan State University)
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56
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Poster session (New facilities, instruments and tools)
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63
Plasma Induced Variation of Bound State β-Decay Rates in PANDORA
PANDORA (Plasmas for Astrophysics, Nuclear Decay Observations and Radiation for Archaeometry) is an upcoming facility at INFN - LNS aiming to use an electron cyclotron resonance ion source (ECRIS) as a compact magnetoplasma to measure in-plasma $\beta$-decay lifetimes of radioisotopes. Decay rates are susceptible to changes in atomic configuration of the parent and daughter systems and are consequently modified inside plasmas due to the surrounding electron cloud, ion charge state distribution (CSD) and level population distribution (LPD). Since the CSD and LPD are strongly non-homogeneous in ECRIS, so are the decay rates, and calculating them is a complex process involving sequential simulations modelling space-resolved properties of electrons, ions and nuclei respectively. We present here a detailed study of the plasma induced nuclear lifetime variation, taking as a test case the orbital electron capture of $^7$Be in a range of plasma density and temperatures. The results confirm the contribution of the atomic configuration to the decay rate and underline the importance of precisely calculating ion CSD/LPD. Using a Particle-in-Cell Monte Carlo (PIC-MC) code to model ECR dynamics, we extend the analysis to a realistic laboratory plasma and demonstrate expected spatial gradients of $^7$Be decay rates in the plasma chamber.
Speaker: Bharat MISHRA (INFN-LNS and University of Catania) -
64
A novel approach to nuclear and astrophysical studies using a laboratory plasma: the PANDORA project
Theoretical predictions and past experiments on highly ionized atoms have shown that the β-decay lifetime can be modified even by several order of magnitudes relative to the value observed in neutral atoms due to the opening of a new decay channel called bound-state β-decay [1,2]. The effect of this variation is particularly relevant for those nuclei placed at the branching point of the s-process. A change in their lifetime would lead to a modification of the nucleosynthesis yield of elements produced accordingly to the competing beta-decay and neutron capture rates.
The PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) project aims to measure, for the first time, possible variations of in-plasma β-decay lifetimes in selected isotopes of astrophysical interest as a function of the thermodynamical conditions of the in-laboratory controlled plasma environment.
The new experimental approach consists of creating and confining a plasma whose main features can mimic specific stellar-like conditions and mapping the evolution of the nuclear lifetime as a function of plasma density and temperature which affect the ions’ charge state distribution [3]. To achieve this goal a dedicated plasma trap, based on a superconducting magnetic system where the radionuclides can be maintained in dynamical equilibrium for weeks, has been designed and is under construction at INFN – Laboratori Nazionali del Sud (Catania, Italy). The β-decay events will be tagged by detecting the γ-ray emitted by the daughter nuclei populated in the decay process using an array of 14 HPGe detectors placed around the trap. Plasma parameters will be monitored online and measured through an innovative non-invasive multi-diagnostic system which will work synergically with the γ-ray detection system and will allow to correlate plasma thermodynamic properties with the in-plasma β-decay lifetime [3].
Three physics cases were selected for the first PANDORA experimental campaign: 134Cs, 94Nb, and 176Lu. The sensitivity of the PANDORA setup to the expected variations of the nuclear lifetimes of the selected isotopes was evaluated through GEANT4 simulations. Results indicate that the designed setup is able to map the evolution of the nuclear lifetime variation as a function of the plasma parameters, with at least a 3σ level of significance, within a range of experimental run duration varying from a few days to about 3 months, depending on the initial value of the lifetime and the amount of relative variation observed.
The PANDORA plasma trap can be also employed for measuring opacity and optical properties of under-dense and low-temperature plasma relevant for kilonovae study. Preliminary results of the tests performed at the LNS using the compact Flexible Plasma Trap (FPT) will be presented [4].[1] Takahashi K., Yokoi, K., Atomic Data Nucl. Data Tables 36, 375 (1987)
[2] Jung M., et al., Phys. Rev. Lett. 69, 2164 (1992)
[3] Mascali D. et al., Universe 8, 80 (2022)
[4] Pidatella A., et al., Front. Astron. Space Sci. 9:931744 (2022)Speaker: Bharat MISHRA -
65
A study of 14O via 10C+alpha elastic scattering: evidence of alpha clustering
We have studied the structure of the proton-rich 14O nucleus by performing the 10C + α elastic scattering measurement at the CRIB facility (CNS, the university of Tokyo). Recently, the cluster nature for some resonances was identified in the mirror nucleus 14C via the 10Be + α reaction (1). A preliminary Resonating Group Method (RGM) calculation has suggested that also the 10C + α system may present resonances with a large reduced width, an indication of clustering effects. The radioactive beam of 1OC was produced at CRIB using the 10B(p,n)10C reaction, using a 10B primary beam with energy 69.9 MeV (AVS cyclotron, RIKEN). The primary target was H2 at 400 Torr and 77K. The secondary beam 10C was produced at 36 MeV with a beam purity better than 97%. The gas chamber was filled with helium gas at 650 Torr and sealed with the Mylar window. Three DeltaE-E silicon detector telescopes were used in the gas chamber at different angles.
By measuring the protons and the α particles, a complex resonant structure for 14O was observed in the excitation energy region 13-18 MeV. By performing an R-matrix analysis of the elastic scattering data at several angles, some evidence of alpha clustering in 0+ and 2+ states has been observed, in fair agreement with the microscopic cluster model.
A better understanding of the nuclear structure of this nuclear mass region is relevant for future nuclear astrophysical studies.(1) H. Yamaguchi et al., Physics Letters B 766, 11 (2017)
Speaker: Prof. Michele SFERRAZZA (Université Libre de Bruxelles) -
66
Development and Status of the In-Flight Fragment Separator at RAON
The Rare isotope Accelerator complex for ON-line experiments (RAON) is a heavy ion accelerator facility that provides both stable and rare isotope (RI) beams for basic and applied science research. The in-flight fragment (IF) separator of RAON, the main device for producing RI beams, is under development. In order to efficiently produce RI beams by using in-flight fission of uranium beams as well as projectile fragmentation reactions, the IF separator is designed to have angular acceptance and momentum resolution of ±40 mrad and ±3%, respectively. The IF separator consists of a target, beam dump, magnets, and detector systems. The high-power target and beam dump for the 80 kW primary beam were fabricated using graphite. The IF magnet system consists of a total of 8 dipole magnets, 15 sets of quadrupole magnet triplet, 2 sextupole magnets, and power supply systems. Fabrication of all IF magnets have been completed and on-site installation is in progress. In addition, detectors for particle identification (PID) and data acquisition (DAQ) systems were installed at the focal planes of the IF separator. The development status of IF separator is briefly introduced.
Speaker: Dr Do Gyun KIM (Institute for Basic Science) -
67
Studying the $^{12}$C($^{12}$C,$\alpha$)$^{20}$Ne reaction at stellar energies using a novel technique
The $^{12}$C+$^{12}$C fusion reaction plays an important role in various astrophysical models, such as type Ia supernova, superburst, and the evolution of massive star. The direct measurements are limited by backgrounds at energies above E$_{\rm c.m.}$=2.1 MeV. To overcome this limitation, we have developed a novel technique to study the $^{12}$C($^{12}$C,$\alpha$)$^{20}$Ne reaction by using a time projection chamber. Preliminary results will be presented in this presentation.
Speaker: Xiaodong TANG (Institute of Modern Physics, CAS) -
68
Current status of KoBRA at RAON
A multi-purpose experimental instrument, called KoBRA (Korea Broad acceptance Recoil spectrometer and Apparatus), was constructed at the Institute for Rare Isotope Science (IRIS), as a part of the RAON facility in Korea. Stable or rare isotope (RI) beams can be produced using Electron Cyclotron Resonance (ECR) ion sources or the Isotope Separation On-Line (ISOL) system at RAON, and these beams can be delivered to KoBRA at energies of 1 − 40 MeV per nucleon via the SuperConducting Linear
accelerator 3 (SCL3). Secondary RI beams can be produced by quasi-projectile fragmentation reaction, and KoBRA will be utilized to generate these RI beams for the studies of nuclear reaction, nuclear structure, and nuclear astrophysics.
KoBRA is currently under beam commissioning phase, and the first test with 40Ar stable ion beam was completed in June 2023. In this presentation, we report on the recent activities of KoBRA from its construction to beam commissioning, together with the detailed design of ion optics and detection system. Additionally, the results from the first beam test will be presented.Speaker: Mr Dong Geon KIM (Institute for Rare Isotope Science, Institute for Basic Science, Hanyang University) -
69
Simulation Study of Neutron Production for NDPS at RAON
Nuclear Data Production System (NDPS) is one of the experimental systems at the Rare isotope Accelerator complex for ON-line experiments (RAON). It provides high-energy neutrons up to tens of MeV. The primary objective of NDPS is to accurately measure the neutron-induced nuclear cross sections, particularly for the neutron energy extending up to tens of MeV region. A beam commissioning of NDPS is scheduled for 2024. Ion beams, such as H, 2H, 16O, and 40Ar, are accelerated from SuperConducting Linac 3 (SCL3) and transported to the NDPS target room. High-energy neutrons will be produced by bombarding an ion beam into the neutron production target at the NDPS target room and delivered to users for the experiments.
For the preparation of forthcoming beam commissioning, simulation studies are performed to calculate neutron productions using the Monte Carlo particle transport codes, namely MCNPX, FLUKA and PHITS. By analyzing the simulation results of various combinations of the ion beams target materials and comparing with available benchmark measurements, an optimal pairing of ion beam and target is proposed for the beam commissioning.Speaker: Jaesung KIM (Institute for Rare Isotope Science, Institute for Basic Science) -
70
Recent progress of Nuclear Data Production System at RAON
A fast neutron facility, called Nuclear Data Production System (NDPS), was constructed for nuclear science and applications at RAON (Rare Isotope Accelerator complex for ON-line experiments) in Korea. NDPS provides neutron beams not only for nuclear data measurements but also for other applications. NDPS is designed to provide both white and mono-energetic neutrons, using 98 MeV deuteron and 20 – 83 MeV proton beams with a thick graphite and thin lithium targets, respectively. Neutron energy is determined by employing the time-of-flight (TOF) technique, along with a pulsed deuteron (or proton) beam with a repetition rate of less than 200 kHz. Fast neutrons are produced in the target room and are guided to the TOF room through a 4 m long neutron collimator consisting of iron and 5 % borated polyethylene. In the TOF room, a gas-filled Parallel Plate Avalanche Counter (PPAC) with a Th-232 layer and EJ-301 liquid scintillation detectors are installed to measure the neutron flux. The beam commissioning for NDPS is scheduled for 2024. The recent progress of NDPS will be reported, together with our plan.
Speaker: Cheolmin HAM (Institute for Rare Isotope Science, Institute for Basic Science) -
71
Multi-reflection time-of-flight mass spectrometer (MRTOF-MS) at RAON
Nuclear mass is known as crucial information to determine the nuclear synthesis pathways occurring in specific stellar environments. These pathways significantly affect the isotopic abundance observed from astronomical observatories. In other words, the compiled mass database, provided through precise measurements, aids in the development of stellar evolution models and enables a deeper understanding of the evolution of stars.
A novel mass measurement device, the Multi-Reflection Time-of-Flight Mass Spectrometer (MRTOF-MS), is employed to study the nuclear mass of rare isotopes provided by RAON (Rare isotope Accelerator complex for ON-line experiments).
Currently installed in the ISOL beam line, the MRTOF-MS thermalizes the RI beams with low energy of less than 60 keV using a helium-buffer gas catcher. It minimizes the emittance of the ion bunches in the trap system and ultimately analyzes them after a few hundred reflections inside the MRTOF analyzer.
The entire system has been optimized using offline ion sources, and a high resolving power of around 100,000 has been achieved within less than 10 ms. The system is in the process of preparation for commissioning with an RI beam transported from the ISOL system.
In this presentation, the current status of the RAON MRTOF-MS, as well as future plans.Speaker: G. OH (Institute for Rare Isotope Science (IRIS), Institute for Basic Science (IBS)) -
72
Capacitive pick-up monitor for the low-energy experimental system at RAON
The Rare Isotope Accelerator Complex for ON-line Experiments (RAON) provides both stable ion (SI) and rare isotope (RI) beams with wide energy ranges for nuclear physics research and other applications. Ion beams with energies up to a few tens of MeV/nucleon will be delivered to the low-energy experimental systems: the Korea Broad Acceptance Recoil Spectrometer and Apparatus (KoBRA) and the Nuclear Data Production System (NDPS). Due to the long beam transport line from the end of the Superconducting Linac3 (SCL3) to KoBRA, a re-bunching system was installed in the middle of the SCL3-KoBRA beam transport line for longitudinal focusing. Similarly, a Half Wave Resonator, in the middle of the SCL3-NDPS beam transport line, can be used as a re-buncher to provide a longitudinally compressed ion beam at the NDPS target room.
To verify the performance of the re-bunchers, the bunch length should be measured with and without the re-bunchers. Therefore, we optimized a capacitive pick-up monitor to measure the beam shape and arrival time at the target position without causing beam disruption. After finalizing the optimized design, we proceeded to manufacture and test the capacitive pick-up monitors. The beam test and installation are scheduled for the end of 2023.
Speaker: Donghyun KWAK -
73
Development of Low-pressure Gas TPC for Stellar Nucleosynthesis Reactions
We develop an active-target Time Projection Chamber (aTPC) operated in a low-pressure, strong magnetic field. The aTPC comprises a cathode plane, four field-cage planes, a gating GEM (Gas Electron Multipliers) plane, a triple GEM structure, and a pad plane. The pad plane covers 10 x 10 cm2 with 1000 3x3 mm2 square pads. The construction of the detector is in progress, and the expected performance is verified using Geant4 and Garfield++ simulation. We will primarily focus on the cross-section measurement for oxygen production from the 12C(α,γ)16O reaction and potassium destruction through the reverse 37Cl(α,n)40K and 40Ar(p,n)40K reactions. This talk will present the current R&D status.
Speaker: Haein LEE (Korea University) -
74
Development of a LaBr3(Ce) detector array for high-energy gamma-ray measurement
We have developed a LaBr3(Ce) detector array, the HANULball, for measuring high-energy gamma rays from nucleosynthesis reactions near 10 MeV. The HANULball prototype comprises eight LaBr3(Ce) detectors arranged on the surfaces of a truncated cuboctahedron structure. Each LaBr3 crystal has a diameter of 50 mm and a length of 75 mm. The prototype array uses 2-inch photomultiplier tubes to detect scintillation light. We tested the prototype performance using a 60Co radioactive source and proton capture gamma rays from the Al(p, gamma)Si reaction from Ep=2.030 to 2.080 MeV at the tandem ion accelerator, KIST. This talk will present the preliminary results of the LaBr3 detector performance over a wide range of gamma-ray energy.
Speaker: Sungjune LEE (Korea University) -
75
ChETEC-INFRA: An EU-supported Starting Community of Research Infrastructures for Nuclear Astrophysics, 2021-2025
ChETEC-INFRA networks complementary types of research infrastructures to study the origin of the chemical elements in the cosmos: nuclear laboratories supply data on reactions of astrophysical interest, optical telescopes and accelerator mass spectrometers collect elemental and isotopic abundance data, and high-performance computing facilities perform stellar structure and nucleosynthesis calculations. The Transnational Access program of ChETEC-INFRA offers access to 13 European facilities, free of charge and open to scientific users worldwide. Joint Research Activities aim to improve usability and reduce barriers of access for efficient utilization of these facilities, and Networking Activities focus on strengthening networks within the scientific community using such facilities. An overview of the activities of ChETEC-INFRA, its transnational access program, activities and selected results will be presented. – Supported by the European Union (Horizon2020), grant agreement no. 101008324 (ChETEC-INFRA).
Speaker: Axel BOELTZIG (Helmholtz-Zentrum Dresden-Rossendorf (HZDR)) -
76
The 12C(p,g)13N reaction S-factor and Er = 422 keV resonance study at Felsenkeller facility.
The $^{12}$C(p,$\gamma$)$^{13}$N is the kick off reaction of the CNO cycle, active in massive star core Hydrogen burning and RGB and AGB star H-shell burning, at typical temperatures between 0.02 and 0.1 GK. The $^{12}$C(p,$\gamma$)$^{13}$N reaction plays a key role in many scenarios, being the $^{13}$N decay one of the solar neutrino source and the main responsible for the $^{13}$C pocket in AGB stars, crucial ingredient for s-process. Moreover the $^{12}$C/$^{13}$C abundance ratio, observed in presolar grains, stellar atmosphere and in the interstellar medium, is a powerful tracer of mixing processes and of the Galactic chemical evolution.
Extrapolation of the $^{12}$C(p,$\gamma$)$^{13}$N reaction $S$-factor down to astrophysical energies is dominated by the direct capture contribution and the tail of a broad resonance at $E_{r}$ = 422 keV. Data below 400 keV are poorly constrained, with available data scattering in a 30\% band. Moreover a recent measurement performed at LUNA reported results in tension with literature data. Concerning the 422 keV resonance only few extensive studies are available in literature, resulting in poorly constrained resonance parameters, as radiative width and energy, which were proved to be crucial in determining the transition from CNO to Hot CNO cycle, active in explosive scenarios.
A new direct measurement was performed at the shallow underground Felsenkeller facility in the energy range $E_{cm}$ = 320-620 keV, allowing to extensively study the 422 keV resonance and to overlap with LUNA range. The experiment was performed irradiating two evaporated carbon targets with 10 $\mu$A molecular beam. The $\gamma$-rays from $^{12}$C(p,$\gamma$)$^{13}$N reaction were detected by mean of five HPGe detectors, located at different angles to check also the angular distribution.
In the talk details of the experimental setup, analysis and preliminary results will be described.Speaker: Axel BOELTZIG (Helmholtz-Zentrum Dresden-Rossendorf) -
77
A new underground measurement of the $^{14}$N(p,$\gamma$)$^{15}$O reaction at Bellotti Ion Beam Facility \\
An accurate understanding of the slowest reaction of the CNO cycle, the $^{14}$N(p,$\gamma$)$^{15}$O, is crucial for estimating the lifetimes of massive stars and globular clusters, as well as determining the CNO neutrino flux from the Sun. Despite the efforts of many groups over the years, including pioneering underground measurements made by the LUNA collaboration, this reaction remains the predominant source of uncertainty when determining solar chemical composition.
The installation of a new 3.5 MV accelerator in the Bellotti Ion Beam Facility of the Gran Sasso National Laboratories (LNGS) will provide unprecedented opportunities for the nuclear astrophysics community. As a pilot project at this new facility, the LUNA collaboration is conducting a $^{14}$N(p,$\gamma$)$^{15}$O experiment, focused on measuring the excitation function and angular distribution using improved solid targets, optimized to limit the beam-induced background contributions. The aim of this renewed measurement is to provide high-quality differential cross section data between 0.3 and 2.0 MeV, which may give new insights and strengthen the knowledge of this fundamental reaction.
Speaker: Alessandro COMPAGNUCCI (Gran Sasso Science Institute) -
78
Development of a low-background neutron detector array
$^{13}$C($\alpha$,n)$^{16}$O is the dominant neutron source of the s- and i-processes. The cross section of this reaction is extremely low at stellar energies(~10$^{-14}$ Barn), which brings large errors of the measurements and makes it difficult to constrain the theoretical extrapolation.
To precisely measure the cross section of the $^{13}$C($\alpha$,n)$^{16}$O reaction, we designed a detector array comprising 24 $^{3}$He proportional counters. The counters were embedded in a polyethylene cube, which was shielded with 7% borated polyethylene layer. The neutron background measured at China Jinping Underground Laboratory(CJPL) was as low as 4.5(2) counts/h, 265 times lower than the result of the ground measurement.
The detection efficiency of the array for neutrons was determined in the range of 0.1MeV to 4.5 MeV, which was carried out with the 3 MV tandem accelerator at Sichuan University and Monte Carlo simulations. Future studies are expected to focus on further improvement of the efficiency and accuracy by measuring the angular distribution of the $^{13}$C($\alpha$,n)$^{16}$O reaction.
Speaker: Taoyu JIAO (Institute of Modern Phuysics)
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63
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Poster session (Novae and X-ray bursts, Type IA supernova and the p-process)
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79
Study of the $^{60}Ga(\beta^{+})^{60}Zn$ decay of for the Astrophysical rp process
One of the goals of nuclear astrophysics is to understand the various astrophysical events occurring in the cosmos.
The most common stellar explosions observed in our galaxy are Type I X-ray bursts (XRB1).
The isotopic abundances obtained from the astrophysical models of XRB1 depend strongly on a number of nuclear reaction rates, occurring both on the surface and inside the crust by the buried ashes.
The nuclear burning that creates these ashes is called the rapid proton (rp) capture process.
Investigating the rp process enhances our understanding of the dynamics of neutron stars and features of XRB1 spectra.
The nuclear reaction flow of the rp process is sensitive to the $\beta+$ decay properties of the nuclei involved, and the experimental study of such properties is of significant importance.
In this study, total absorption spectroscopy (TAS) analysis was performed for the $^{60}Ga(\beta+)^{60}Zn$ decay.
This experiment was performed at the National Superconducting Cyclotron Laboratory (NSCL).
In this presentation, the extracted beta feeding intensity will be discussed, along with a comparison to theoretical shell model and QRPA calculations.Speaker: Gerard OWENS-FRYAR (FRIB) -
80
Evaluation of 19Ne nuclear structure with a Bayesian approach
The 15O(α, γ)19Ne and 18F(p, α)15O reaction rates at stellar temperatures have significant impacts on the dynamics in x-ray bursts, novae explosions, and heavy element synthesis. Due to its importance, the nuclear structure of the compound nucleus 19Ne, which determines the reaction rate, has been widely investigated. Collecting the available data from experimental measurements, Nesaraja et al. had previously evaluated the nuclear structure of 19Ne above the proton-threshold energy [Phys. Rev. C 75, 055809 (2007)], which provided useful information for reaction rate calculations. Because many new experiments have been performed since that evaluation, the nuclear structure properties of 19Ne needs to be updated. In this work, the results from the latest measurements are compiled and then evaluated employing a novel Bayesian approach to integrate the results from independent measurements. By demonstrating the statistical and physical meanings of the priors for resonance parameters and likelihoods for previous experimental results, the posterior (i.e., updated) distributions of the resonance parameters could be obtained. These posteriors will be presented and directly used as probability density functions for Monte Carlo reaction rate calculations.
Speaker: Sohyun KIM (Sungkyunkwan University) -
81
26Si(α, α)26Si measurement for the astrophysical 26Si(α,p)29P reaction rate
The study of the $^{26}$Si($\alpha$,$p$)$^{29}$P reaction rate is essential for understanding X-ray burst phenomena. It is believed that the heavy elements up to the Sn-Sb-Te region can be synthesized during the burst. Since 26Si is considered to be a waiting point during the burst, the $^{26}$Si($\alpha$,$p$)$^{29}$P reaction rate is believed to be one of the most significant reactions that affects nucleosynthesis. To study the $^{26}$Si($\alpha$,$p$)$^{29}$P reaction rate, the properties of energy levels in the $^{30}$S were studied through the $^{26}$Si($\alpha$,$\alpha$)$^{26}$Si reaction measurement. The radioactive 26Si beam was produced through the $^{3}$He($^{24}$Mg,$n$)$^{26}$Si reaction at the Center for the Nuclear Study Radioactive Ion Beam Separator (CRIB) of the University of Tokyo. By adopting the thick target method, the resonant states were observed over the wide energy range of E$_{x}$ = 12 - 16 MeV for the first time. By comparing the empirical excitation function and theoretical calculation results with the SAMMY8 code, the properties of $^{30}$S energy levels were constrained. The astrophysical $^{26}$Si($\alpha$,$p$)$^{29}$P reaction rate was updated accordingly. The details of the results will be discussed.
Speaker: Minju KIM (Department of Physics, Sungkyunkwan University) -
82
Study of mirror resonant reactions by TTIK approach
Developments of the rare beam acceleration have opened new opportunities for study of mirror resonance reactions. Namely, comparison of the results of the mirror resonance reactions gives the opportunity to understand nuclear structure deeper.
$\quad$ Understanding the nuclear structure of $^{19}F$ and $^{19}Ne$ is crucial in comprehending the clustering structure around mass $A=20$. Previously, experiment with $\alpha+^{15}N$ scattering was conducted only by Smotrich et al. [1] in 1960, covering broad angles and energy range. But the analysis of excitation functions with several channels and overlapping resonances has not been performed [1].
$\quad$ We present the results of R-matrix analysis on Smotrich data [1] and our recent data on $\alpha+^{15}N$ resonant interaction obtained by the Thick Target Inverse Kinematics (TTIK) [2,3] method at DC-60 cyclotron in Astana. New R-matrix parameters were obtained from analysis of $^{19}F$ and then used to fit the mirror 19Ne spectrum from [4] in the same energy range. R-matrix analysis of the excitation function for the mirror $\alpha+^{15}O$ elastic scattering was done based on new results for $^{19}F$ [5,6]; both experiments were performed using the TTIK method.
$\quad$ TTIK approach for data acquisition in mirror nuclear reactions allows to obtain new spectroscopic information.References:
[1] H. Smotrich, K. W. Jones, L. C. McDermott, and R. E. Benenson, Elastic scattering of $\alpha$ particles by $^{15}N$, Phys. Rev. 122, 232 (1961).
[2] K. Artemov, O. Belyanin, A. Vetoshkin, Effective method of investigation of $\alpha$-cluster states, Soviet Journal of Nuclear Physics ,Ussr 52, 408, 634–639, (1990).
[3] A. K. Nurmukhanbetova, V. Z. Goldberg, D. K. Nauruzbayev, G. V. Rogachev, M. S. Golovkov, N. A. Mynbayev, S. Artemov, A. Karakhodjaev, K. Kuterbekov, A. Rakhymzhanov, Z. Berdibek, I. Ivanov, A. Tikhonov, V.I. Zherebchevsky, S. Y. Torilov, and R. E. Tribble, Implementation of TTIK method and time of flight for resonance reaction studies at heavy ion accelerator DC-60,NIM A 847, 125, (2017).
[4] D. Torresi, C. Wheldon Tz. Kokalova, S. Bailey, A. Boiano, C. Boiano, M. Fisichella, M. Mazzocco, C. Parascandolo, D. Pierroutsakou, E. Strano, M. Zadro, M. Cavallaro, S. Cherubini, N. Curtis, A. Di Pietro, J. P. Fernandez-Garcia, P. Figuera, T. Glodariu, J. Grebosz, M. La Cognata, M. La Commara, M. Lattuada, D. Mengoni et al., Evidence for $^{15}O+\alpha$ resonance structures in $^{19}Ne$ via direct measurement, Phys. Rev. C 96, 044317 (2017)
[5] Goldberg, V.Z., Nurmukhanbetova, A.K., Volya, A.,Serikbayeva, G.E., Rogachev, G.V. $\alpha$-cluster structure in $^{19}F$ and $^{19}Ne$ in resonant scattering. Physical Review C, 2022, 105(1), 014615
[6] Volya, A., Goldberg, V.Z., Nurmukhanbetova, A.K., Nauruzbayev, D.K., Rogachev, G.V. Lowest-energy broad $\alpha$-cluster resonances in $^{19}F$,Physical Review C, 2022, 105(1), 014614Speaker: Gulfairuz SERIKBAYEVA (Nazarbayev University Research and Innovation System, Astana, Kazakhstan) -
83
Direct Measurement of the 14O(α,p)17F Cross Section
14O(α,p)17F is one of the important reactions that strongly affects the light curves of Type Ⅰ X-ray burst models [1]. The reaction rate is known to determine the break-out path from the hot CNO cycle to the rp-process at sufficiently high temperatures (T9 > 0.5) [2]. However, its large uncertainty due to the lack of experimental measurements causes difficulties in the precise demonstration of astrophysical observables.
In order to constrain the reaction rate, a direct measurement of the 14O(α,p)17F cross section was performed at CNS RI beam separator (CRIB), RIKEN. A 14N beam with the energy of 8.40 MeV/u and H2 gas cell target were used to produce the 14O beam. As a reaction target and charged particle detector, the Texas Active Target Time Projection Chamber (TexAT) was used [3]. The detector was developed at Texas A&M University, and upgraded to TexAT_v2 at the Center for Exotic Nuclear Studies (CENS), Institute for Basic Science (IBS) to optimize the detection efficiency for the (α,p) cross section measurement. The energy and position resolution of detected charged particles from the reaction are enhanced thanks to the three-dimensional tracking of the particles. Along with segmented silicon and CsI(Tl) detectors around the field cage, the TexAT enables measuring more precise cross sections as a function of center-of-mass energy. In order to manage about 2500 channels from various detectors, the GET electronics is used with the GANIL data acquisition system [4].
Details of the experimental setup and the results of preliminary analysis of the experiment will be discussed.References
[1] R. H. Cyburt et al., Astrophys. J. 830, 55 (2016).
[2] R. K. Wallace and S. E. Woosley, Astro. J. Suppl. Ser. 45, 389 (1981).
[3] E. Koshchiy et al., Nucl. Inst. and Meth. A 957, 163398 (2020).
[4] E. C. Pollacco et al., Nucl. Inst. and Meth. A 887, 81 (2018).Speaker: Chaeyeon PARK (EWHA Womans University / CENS(IBS)) -
84
Direct measurement of the ${}^{26}$Si($\alpha$, p)${}^{29}$P reaction at CRIB for the nucleosynthesis in the X-ray bursts
In the X-ray bursts, the ${}^{26}$Si($\alpha$, p)${}^{29}$P reaction rate is considered to have a great impact on the light curve. However, there were insufficient experimental data for this reaction because of technical difficulties. In order to measure the cross section of the reaction, a direct measurement was performed at the CNS RI beam separator (CRIB). CRIB produced a ${}^{26}$Si beam with a typical intensity of 3.2 $\times$ 10${}^4$ pps and a purity of 29%, which bombarded the ${}^4$He gas target. The ${}^{26}$Si($\alpha$, p)${}^{29}$P reaction was measured up to the center-of-mass energy of about 7.5 MeV using the thick gas target method. This energy region corresponds to about T = 3 GK of the Gamow energy. In spite of the large number of background events and the large statistical error, an upper limit on the reaction cross section was obtained, which was 0.134 times that of the NON-SMOKER statistical model.
This is the first experimental evaluation by direct measurement. Therefore, the result are useful to compare experimental and theoretical values at higher temperature and to constrain the ${}^{26}$Si($\alpha$, p)${}^{29}$P reaction rate and the X-ray burst light curve model.The analysis method and the results will be discussed.
Speaker: Kodai OKAWA (CNS, the University of Tokyo) -
85
Thermonuclear reaction rate sensitivity study for primordial nova nucleosynthesis
Classical novae are common cataclysmic events in the Galaxy involving a binary system. In the early Galaxy these explosions proceeded differently, mainly due to the accretion of sub-solar material onto the white dwarf. It has been proposed that these primordial novae explosions produce a different abundance pattern compared to their classical counterparts [1]. In particular, the nuclear flows extend up to the Cu-Zn region, compared to classical novae, which have an endpoint around Ca. To study the impact of the nuclear physics uncertainties in primordial novae nucleosynthesis we performed a sensitivity study, varying all the relevant reactions in the network within their uncertainty using a Monte Carlo approach [5]. We find nuclear reactions which uncertainties affect the production of intermediate mass nuclei under primordial novae conditions. These reactions need to be measured experimentally in stable and radioactive beam facilities to reduce their uncertainties.
*This work is supported by U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE-SC0017799 and Contract Nos. DE-FG02-97ER41033 and DE-FG02-97ER41042.
References
[1] J. José et al., Astrophys. J 622, L103 (2007).
[2] A.L. Sallaska et al., Astrophys. J Suppl. Ser. 207, 18 (2013).
[3] R. Longland et al., Nucl. Phys. A 841, 1 (2010).
[4] C. Iliadis and A. Coc, Astrophys. J 901, 127 (2020).
[5] A. Psaltis et al. (in preparation).Speaker: Thanassis PSALTIS (NCSU/TUNL) -
86
Lifetime measurement of the dominant 22Na (p, gamma) 23Mg resonance in novae
$^{22}$Na (T$_{1/2}$ = 2.6 y) is of high interest for space-based γ-ray astronomy because its direct observation could constrain classical nova models. Although the characteristic 1275 keV β-delayed γ decay radiation has not been observed yet, future γ-ray telescopes may detect the decay with high sensitivity. To link these observations with nova model predictions, nuclear data are needed. The $^{22}$Na(p, γ) $^{23}$Mg reaction destroys $^{22}$Na produced during a nova. In the literature, there are discrepancies of one order of magnitude in the experimentally determined strength of the E$_{R}$=204 keV resonance important at nova temperatures. This affects predictions of the ejected yield substantially.
The resonance strength can be determined by measuring the proton branching ratio and the lifetime of the corresponding E$_{x}$=7.785 MeV excited state in $^{23}$Mg.
With the Doppler-Shift Lifetime (DSL2) setup at TRIUMF-ISAC-II a new effort was started to measure the lifetime of this exited state. Excited states in $^{23}$Mg are populated by the $^{24}$Mg ($^{3}$He, α) $^{23}$Mg reaction with a 75 MeV $^{24}$Mg beam. Using the Doppler-Shift Attenuation Method (DSAM), deexcitation γ-rays are detected to perform line-shape analysis and infer the lifetime. This contribution will present the DSAM method and results from a preliminary measurement.The authors acknowledge the generous support of the Natural Sciences and Engineering Research Council of Canada. TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada. The GRIFFIN infrastructure was funded jointly by the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the British Columbia Knowledge Development Fund, TRIUMF, and the University of Guelph.
Speaker: Louis WAGNER (TRIUMF) -
87
Nuclear astrophysics study using SNACK at KoBRA
KoBRA (KOrea Broad acceptance Recoil spectrometer and Apparatus) [1] is a low energy nuclear physics facility at RAON (Rare isotope Accelerator complex for ON-line experiments) [2]. In its early phase of operation, KoBRA will produce RI beams with energies of 5 to 10 MeV/u from stable ion beams (10 ~ 40 MeV/u) delivered from the superconducting linear accelerator SLC3 of RAON. Transfer reaction measurements with RI beam are a powerful tool to extract spectroscopic information such as spins, parities, and spectroscopic factors. With this information, the thermonuclear reaction rates in explosive stellar environments such as novae, X-ray bursts, and supernovae can be studied. Therefore, the silicon detector system SNACK (Silicon detector array for Nuclear AstrophysiCs study at KoBRA) [3] has been developed by IRIS (Institute for Rare Isotope Science) for (d,p) transfer reaction measurements at KoBRA. By measuring protons produced in the reactions with SNACK and the trajectories of RI beams with upstream PPAC (Parallel Plate Avalanche Counter) detectors, excited energy levels can be reconstructed to extract spectroscopic information. In order to investigate the feasibility of the (d,p) reaction measurement using SNACK at KoBRA, the 18Ne(d,p)19Ne reaction measurement was simulated for study of the 18F + p system in nova explosions. In this presentation, details of the detector system development and results of the simulation will be presented.
[1] K. Tshoo et al., Nucl. Instrum. Methods Phys. Res. B 376 (2013) 188.
[2] D. Jeon et al., J. Korean Phys. Soc. 65 (2014) 1010.
[3] M.S. Kwag et al., Nucl. Instrum. Methods Phys. Res. B 541 (2023) 42.Speaker: Dr Minsik KWAG (IRIS, IBS) -
88
Igniting the Superburst on KS1731-260
Superbursts are rare, energetic explosions observed from accreting neutron stars in low-mass X-ray binaries. Associated with the unstable ignition of carbon, superbursts are challenging to model as their energetics are too low and recurrence times too short to be easily accommodated with theoretical models of the neutron star crust and the standard extrapolation of the C12+C12 cross-section to astrophysical energies. The quasi-persistent neutron star transient KS1731–260 is a particularly good site to probe these enigmatic bursts since its quiescent luminosity has been monitored over 20 years, which provides good constraints on the temperature of the neutron star's outer layers. In addition, it had one observed superburst while actively accreting in 1996. We explore the ignition of carbon on KS1731–260 using different C12+C12 cross-sections. We find tension between the burst depth in our models and the depth inferred from observations of the superburst indicating greater heating at shallow depths than expected. This discrepancy may be reconciled by either the lack of precision in the measured distance to KS1731–260 or an increase of the C12+C12 cross-section at ~1.5 MeV.
Speaker: Eric BRITT (Michigan State University) -
89
Identifying the Origin of Presolar Grains: Gamma-Spectroscopy of 35Ar
Classical novae are the second most common explosive stellar phenomena in the Universe [1] and, as such, play an important role in the enrichment of the interstellar medium and chemical abundances we observe in the galaxy. One observable, which is key to understanding the processes that drive classical novae, is presolar grains. It is, therefore, important that we are able to characterise the origin of presolar grains based on their isotopic ratios. One issue that remains is being able to distinguish between grains of nova and supernova origin.
It has been suggested that the $^{34}$S/$^{32}$S isotopic ratio could be used, in conjunction with the well-known $^{33}$S/$^{32}$S ratio [2], in order to distinguish between solar and novae presolar grains [3,4]. The abundance of $^{34}$S is dependent on the $^{34g,m}$Cl(p,γ)$^{35}$Ar rp-process reaction rate. To determine this reaction rate, one has to know the energy, spin and parity of the contributing resonances in $^{35}$Ar. The energies of all states above the proton threshold have been measured [3], however, almost all the spins and parities remain unknown.
Here, we report a gamma-spectroscopy measurement of $^{35}$Ar with the aim of observing gamma decay from states above the proton-emission threshold. This experiment was conducted at Argonne National Laboratory’s ATLAS facility. States in 35Ar were populated via the $^{9}$Be($^{28}$Si,2 n)$^{35}$Ar fusion-evaporation reaction. The excited states decay via the emission of gamma rays, which are detected using Gammasphere, in coincidence with the recoils at the focal plane of the Fragment Mass Analyzer (FMA).
This measurement represents the first observation of gamma-decays from states above the proton threshold in $^{35}$Ar and led to more precise measurements of the resonance energies of the key states. The observed gamma-decay branches, along with mirror nuclei comparisons, enable restrictions to be placed on the spin-parity quantum numbers. This enables restrictions to be placed on the $^{34g,m}$Cl(p,γ)$^{35}$Ar reaction rate and the $^{34}$S/$^{32}$S isotopic ratio in novae.
[1] J. José, C. Iliadis, Reports on Progress in Physics 74, 096901 (2011)
[2] A. Parikh, et al., Phys. Lett. B 737, 314-319 (2014)
[3] C. Fry, et al., Phys. Rev. C 91 015803 (2015)
[4] A. R. L. Kennington et al., Phys. Rev. C 103, 035805 (2021)Speaker: Ben REED (University of Surrey) -
90
Direct measurement of the cross section for 102Pd(p,g)103Ag reaction in the p-process
The study of the p-process is of paramount importance in unraveling the origin of heavy elements in the universe. To describe the entire p-nuclei nucleosynthesis process, a comprehensive reaction network involving over ten thousand nuclear reactions is required, and accurate measurements of some key reaction cross sections are essential for determining reaction rates. 102Pd is one of the more than 30 p-nuclei, and the 102Pd(p,g)103Ag reaction is one of its significant destruction reactions. Experimental studies for the p-nucleus 102Pd indicate that the reaction rate for 102Pd(p,g)103Ag is significantly higher than HF predictions. There are significant discrepancies in the available data on the 102Pd(p,g)103Ag reaction cross section in the low-energy regime relevant to nuclear astrophysics. In light of these discrepancies, a direct measurement was carried out to determine the reaction cross section of 102Pd(p,g)103Ag within the energy range of 1.9-2.8 MeV. The measurement was conducted utilizing the 2*1.7 MV tandem accelerator at China Institute of Atomic Energy (CIAE). The latest cross section data were obtained using offline activation measurement technique based on the low background anti-muon and anti-Compton spectrometer in CIAE.
The latest results have extended the cross section of 102Pd(p,g)103Ag to the lowest energy range of proton down to 1.9 MeV. The newly measured cross section data provide valuable experimental references for the calculation of statistical models, particularly in the low-energy regime of interest in nuclear astrophysics. These results contribute to a better understanding of the p-process and its implications for the nucleosynthesis of heavy elements in the universe.Speaker: Fulong LIU (Center for Nuclear Study, the University of Tokyo)
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79
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Poster session (Nuclear properties for astrophysics)
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91
Understanding collective nuclear excitations within microscopic HFB+QRPA calculations
The study of nuclear excitations, particularly collective excitation modes such as the giant resonance (GR) and pygmy resonance (PR), can reveal important characteristics of the underlying nuclear structure. The PR is a fascinating excitation mode that is more prominent in nuclei with an excess of neutrons. This resonance is typically interpreted as a collective motion in which the neutron excess oscillates against a core. It is known to enhance the neutron capture rates, which are crucial for understanding the creation of elements in our universe. However, our knowledge of the low-lying collective excitations remains incomplete despite decades-long efforts to measure and describe collective phenomena. Our inability to include collective effects in reaction calculations affects a range of applications, from nuclear astrophysics to nuclear energy.
In this work, we investigate the low-lying collective excitations in selected Mo isotopes, focusing on the GR and PR modes. Our fully consistent calculations using the Quasi-particle Random Phase Approximation (QRPA) and Hartree-Fock-Bololiubov (HFB) provide valuable insights into the characteristics of these collective excitations. For representative nuclei, we present the electric transition strengths and transition densities, discuss the location of the PR, and investigate the relation between the PR and the neutron excess.Speaker: Eun Jin IN (Lawrence Livermore National Laboratory) -
92
Exploring Stealth Dark Matter on the Lattice
We conduct a numerical study of Stealth Dark Matter (SDM), a composite dark matter (DM) model in SU(4) gauge theory, using the method of lattice gauge theory. Utilizing the fastest supercomputers at Lawrence Livermore National Laboratory, we calculate the baryon-baryon scattering in SDM. In this talk, on behalf of the Lattice Strong Dynamics (LSD) collaboration, we discuss the recent progress and computational challenges in our project focused on SDM baryon scattering.
Speaker: Sungwoo PARK (Lawrence Livermore National Laboratory) -
93
Revisiting the Gamow Factor of Reactions on Light Nuclei
In this presentation, we provides an improved understanding of the penetration probabilities(PPs) in nuclear reactions for light nuclei by rectifying the assumptions utilized in the conventional Gamow factor. The Gamow factor effectively represents PP in nuclear reactions based on two assumptions: particle energy lower than the Coulomb barrier, and the disregard of nuclear interaction potential dependence. However, our findings reveal that these assumptions are invalid for light nuclei. Through calculations that exclude the aforementioned assumptions, we derived a PP that is dependent on the depth of nuclear interaction potential for light nuclei. With the potential depth fitted by experimental fusion cross-sections, we demonstrate that the PPs of light nuclei (D+D, D+T, D+3He, p+D, p+6Li, and p+7Li) exceed the conventional values near the Coulomb barrier. Additionally, we discuss the implications of this modified PP, such as alterations in the Gamow peak energy, which governs the measurement of the energy range of nuclear cross-sections in experiments, and the electron screening effect.
Speaker: Eunseok HWANG (Soongsil University) -
94
Reaching for neutron rich nuclides near N=126 magicity below 208Pb
The neutron-rich unstable nuclei near neutron magic numbers are relatively well studied, far from the stability lineup to the neutron magic number N = 82. However, for the neutron-rich nuclei to the south of 208Pb, there is limited knowledge of the excited states of these nuclei. This arises from the difficulty in producing these nuclei using conventional methods. Even for the known nuclei, only limited information, mostly from decay spectroscopy, is known. The recent multi-nucleon transfer reaction showed promising results with several orders of magnitude larger cross-sections than those for fragmentation reactions.
A new experiment was carried out at GANIL to explore these isotopes of interest using 7MeV/u 136Xe beam and 198Pt target using multi-nucleon transfer reactions. Significant acceptance VAMOS++ magnetic spectrometer and AGATA Ge tracking array were used to measure excited states of nuclides of interest. And several new experimental techniques were implemented in this experiment. First, a second arm detector was newly installed, composed of a vacuum chamber and multi-wire proportional counter to measure the velocity vector of the target-like fragments. Second, four EXOGAM HPGe clover array was installed at the end of the second arm to measure the delayed gamma rays from the excited states of the produced nuclei. Finally, a new method to determine particle identification is under development using a machine learning algorithm, where energy and charge states are determined using supervised machine learning and atomic numbers are determined by the unsupervised learning method. The experiment's preliminary result, such as particle identification with the help of machine learning and gamma-ray spectroscopy neutron-rich nuclei, will be presented.Speaker: Yung Hee KIM (CENS) -
95
Mass measurements of neutron-rich nuclei along the r-process path using Bρ-TOF method
The sensitivity studies of r-process nucleosynthesis performed in recent years [1-3] have pointed out that nuclear masses are of fundamental importance in r-process modeling. The results indicate that independently of the mass models and astrophysical scenarios used, the most sensitive mass regions are along and near the r-process path, particularly around N=50 and N=82 closed shells. Consequently, in our approved experiment with 6.5-days of beam time, we plan to utilize the time-of-flight (TOF) technique at FRIB to measure the masses of 24 neutron-rich nuclei on and around the r-process path beyond the closed shell of N=50 for the first time. Furthermore, the precision of four mass values will be improved. New mass measurements of these neutron-rich nuclei will play a crucial role to understand better the first r-process abundance peak.
The experimental setup includes a 70-m flight path between the ARIS fragment separator and the S800 spectrograph. The TOF will be measured using fast-timing scintillators located at the focal planes of ARIS and S800. The relative measurement of magnetic rigidity, Bρ, will be obtained via position measurement using a microchannel plate detector (MCP) located at the target position of S800. Moreover, we developed a position-sensitive large-area MCP detector system that consists of two MCPs with 120 mm active diameter and delay-line anode [4]. This detector system has the potential to improve the resolution of the Bρ measurement, which is one of the factors currently limiting the mass resolution of the experimental setup.
In this talk, the physics motivation of our measurement, as well as an overview of the experimental setup will be presented. Additionally, we will report the properties and characteristics of the newly developed MCP detector system and future updates.[1] M. Mumpower, et al., Prog. Part. Nucl. Phys. 86, 86 (2016).
[2] A. Aprahamian, et al., AIP Adv. 4, 041101 (2014).
[3] R. Surman, et al., Phys. Rev. C 79, 045809 (2009).
[4] Z. Korkulu et al., Nucl. Instr. Meth. B 541, 232 (2023).Speaker: Zeren KORKULU (Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon, Republic of Korea) -
96
Sensitivity Studies on Type Ia Supernova Observables
Although there is broad agreement that Type Ia Supernovae (SNe Ia) originate from thermonuclear explosions of carbon-oxygen white dwarf stars (WD), the details of the path towards explosion remain uncertain: the degeneracy of the binary system, mass, and chemical composition of the WD, and the explosion mechanism of the SNe Ia. Using the reaction rates in STARLIB [1] we probe the sensitivities of nuclear reactions responsible for the abundance of potential observables in hopes to shed light on some of these uncertainties. This is done by employing a Monte Carlo reaction network method [2] by varying all reaction rates simultaneously according to their rate probability densities in each simulation. The hydrodynamical trajectories were derived from a near-M$_{Ch}$ WD shell model with a 5 x 10$^{-4}$ M He layer surrounding its carbon oxygen core [3]. To take advantage of future early time observations, we focus on both early-time (e.g. gamma ray emitters) and late-time observables (e.g. elemental abundances in ejecta, supernova remnants). Results will be discussed.
*This work is supported by the DOE, Office of Science, Office of Nuclear Physics, under Grants No. DE-FG02-97ER41041 (UNC) and No. DE-FG02-97ER41033 (TUNL).
References
[1] A. L. Sallaska et al. ApJS 207 18 (2013)
[2] C. Iliadis et al. J Phys. G 42, 034007 (2015)
[3] Hoeflich, P. et al. Nuclei in the Cosmos XV. Springer Proceedings in Physics, 219 (2019)Speaker: Minjoo LEE (University of North Carolina Chapel Hill) -
97
Recent theoretical activities in IRIS
In this Poster, we present a few examples of recent theoretical activities in IRIS.
Speaker: Young-Ho SONG (RISP, IBS) -
98
Bubble nuclei with shape coexistence and alpha-decay half-lives in deformed relativistic Hartree-Bogoliubov theory in continuum
After introducing the details of the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), we present our recent results on the bubble nuclei with shape coexistence in isotopes from Hf to Hg and alpha-decay half-lives of W to U. We predict several exotic isotopes that have both bubble configuration and shape coexistence. We also calculate alpha-decay half-lives in DRHBc and compare our results with them from relativistic continuum Hartree-Bogoliubov with spherical symmetry to discuss deformation effects in alpha-decay.
Speaker: Dr Yong-Beom CHOI (Pusan National University) -
99
Comparison study for DJBUU and SQMD, microscopic models to describe Heavy ion collisions
Transport models are microscopic model to describe heavy ion collisions. they let us study nuclear matter properties, which are important to understand such as neutron star. transport models categorized two type, BUU-like and QMD-like model, we have each, DJBUU and SQMD, which are developed for RAON experiments. In this study, we compare the result of simulation using each model.
Speaker: Dae Ik KIM (Pusan National University) -
100
Extraction of Gamow-Teller Strength Using (d,2He) Reaction in Inverse Kinematics
Electron-capture (EC) rates play a key role in core-collapse and thermonuclear supernovae, the crust of accreting neutron stars in binary systems, and the final core evolution of intermediate mass stars. Charge-exchange reactions (CERs) at intermediate energies (~100 MeV) are crucial in extracting information for neutron-rich nuclei as the EC Q-values are positive for such nuclei. The differential cross-sections in CERs at zero momentum transfer are proportional to the Gamow-Teller strength, B(GT), from which the EC rates can be calculated. In a first of a kind experiment, the S800 spectrometer at National Superconducting Cyclotron Laboratory (NSCL) along with Active-Target Time Projection Chamber (AT-TPC) setup was used to run an experiment with ($d$,$^2$He) probe in inverse kinematics to study unstable nuclei. Data from the experiment for the $^{13}$N($d$,$^2$He)$^{13}$C reaction has been analyzed to extract the differential cross-section for ground and excited states to measure the B(GT).
Speaker: Zarif RAHMAN (Michigan State University) -
101
QRPA calculations of weak-interaction rates in stellar conditions
Weak-interaction rates, including beta-decay and capture of electrons from the stellar plasma, are studied under various density and temperature conditions of astrophysical interest. The study focuses on different nuclear mass regions, such as neutron-deficient medium-mass waiting-point nuclei involved in the rp process, neutron-rich medium-mass isotopes involved in the r process, and pf-shell nuclei of special importance as constituents in pre-supernova formations.
The nuclear structure involved in the weak processes is described within a microscopic proton-neutron quasi-particle random-phase approximation with residual interactions in both particle-hole and particle-particle channels on top of a deformed Skyrme Hartree-Fock mean field with pairing correlations. This approach is found to reproduce reasonably well both the experimental beta-decay half-lives and the Gamow-Teller strength distributions measured under terrestrial conditions. Compared to terrestrial half-lives, the stellar ones receive contributions from thermally populated excited states in the decaying nucleus, as well as from electron captures in the stellar plasma. Both effects may modify substantially the weak-decay rates measured in the laboratory.
Speaker: Pedro SARRIGUREN (Instituto de Estructura de la Materia, CSIC) -
102
Identification of metastable isomeric states of Ac-228 with NaI(Tl) crystals
We report the identification of metastable isomeric states of Ac-228 at 6.28 keV, 6.67 keV, and 20.19 keV, with lifetimes of an order of 100 ns. These states were identified with NaI(Tl) crystal detectors of the COSINE-100 dark matter search experiment. The isomeric states are produced through the beta decay of Ra-228, a component of the Th-232 decay chain, with beta Q-values of 39.52 keV and 25.61 keV, respectively. The presence of these states has significant implications for low-energy background modeling in dark matter search experiments due to the low Q-value and the relative abundance of Th-232 and its progeny in low background experiments. In this presentation, we will describe methods and results with the COSINE-100 detectors as well as future prospects for a dedicated measurement of the Ac-228 isomeric states.
Speaker: Kyungwon KIM (Center for Underground Physics, IBS)
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91
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Poster session (Nuclear reaction rates and stellar abundances)
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103
$S$ matrices of elastic $\alpha$-$^{12}$C scattering at low energies in cluster effective field theory
The elastic $\alpha$-$^{12}$C scattering at low energies for $l=0,1,2,3,4,5,6$ is studied in effective field theory. We discuss the construction of the $S$ matrices of elastic $\alpha$-$^{12}$C scattering in terms of the amplitudes of sub-threshold bound and resonant states of $^{16}$O, which are calculated from the effective Lagrangian. The parameters appearing in the $S$ matrices are fitted to the phase shift data below the $p$-$^{15}$N breakup threshold energy, and we find that the phase shifts are well described within the theory.
Speaker: Shung-Ichi ANDO (Sunmoon University) -
104
Analytic expression of triple-$\alpha$ reaction rates by a non-adiabatic three-body model
Triple-$\alpha$ reaction plays a significant role in nucleosynthesis heavier than $^{12}$C and concomitant stellar evolution [1]. The reaction rates of this reaction at the helium-burning temperatures, $T_9 > 0.1$, are dominated by the sequential process via two narrow resonances: $\alpha+\alpha\rightarrow ^8$Be(0$^+_1$), $^8$Be+$\alpha \rightarrow ^{12}$C(0$^+_2$: $E=0.379$ MeV) [2,3], and they have been thought to decide a fate of massive stars up to their supernova explosion. $T_9$ is temperature in the unit of 10$^9$ K; $E$ is the center-of-mass energy to the 3$\alpha$ threshold in $^{12}$C.
In NACRE [2], $^8$Be is assumed to be bound as a particle, and the reaction rates have been estimated by an improved model with the sequential process based on [4,5]. To determine the rates more accurately, the precise experimental decay studies of the 0$^+_2$ resonance have been performed recently (e.g. [6]). The theoretical models have also been being developed during decades. To take account of 3$\alpha$ continuum states distorted by the long-range Coulomb interaction, the methods with hyper-spherical coordinates are used in [7-10], and the Coulomb modified Faddeev method is also adopted in [11]. Whereas $^8$Be continuum states are treated adiabatically in Refs. [9-11], the direct process from ternary continuum states, $\alpha+\alpha+\alpha \rightarrow ^{12}$C, is calculated non-adiabatically in Refs. [7,8]. Although the theoretical models are consistent with each other at the helium-burning temperatures, they make the large difference in the rates below $T_9 = 0.07$. From the comparison between the calculations, Ref. [7] has found that the current reaction rates at $T_9 = 0.05$ can be reduced by about 10$^{-4}$, because of the assumed $^8$Be.
In this presentation, I review the non-adiabatic approach to the triple-$\alpha$ reaction, and provide the derived rates. I use the Faddeev hyper-spherical harmonics and $R$-matrix (HHR$^\ast$) expansion method [7,12,13], and I confirm that the photo-disintegration of $^{12}$C(2$^+_1$($E=-2.835$ MeV) $\rightarrow$ 0$^+$) for $0.15 < E < 0.35$ MeV is 10$^{-15}$ -- 10$^{-3}$ pb order of cross sections. The resultant rates are shown to have the strong temperature dependence below $T_9 = 0.1$, as well as NACRE, and their numerical values are expressed in a simple analytic form [2,14].
[1] F. Hoyle, Astrophys. J. Suppl. Ser. 1, 121 (1954); E.E. Salpeter, Astrophys. J. 115, 326 (1952).
[2] C. Angulo, M. Arnould, M. Rayet, et al., Nucl. Phys. A 656, 3 (1999).
[3] G.R. Caughlan, W.A. Fowler, At. Data Nucl. Data Tables 40, 283 (1988).
[4] K. Nomoto, F.-K. Thielemann, S. Miyaji, Astron. Astrophys. 149, 239 (1985).
[5] K. Langanke, M. Wiescher, F.-K. Thielemann, Z. Phys. A 324, 147 (1986).
[6] D. Dell'Aquila, et al., PRL 119, 132501 (2017); R. Smith, et al., PRL 119, 132502 (2017).
[7] M. Katsuma, to appear in Proc. OMEG16, Communications in Physics, arXiv:2302.03844 (2023).
[8] N.B. Nguyen, F.M. Nunes, I.J. Thompson, PRC 87, 054615 (2013); N.B. Nguyen, F.M. Nunes, I.J. Thompson, E.F. Brown, PRL 109, 141101 (2012).
[9] D.V. Fedorov, A.S. Jensen, PLB 389, 631 (1996).
[10] H. Suno, Y. Suzuki, P. Descouvemont, PRC 94, 054607 (2016).
[11] S. Ishikawa, PRC 87, 055804 (2013); ibid. 90, 061604 (2014).
[12] I.J. Thompson, F.M. Nunes, Nuclear Reactions for Astrophysics, (Cambridge Univ. Press, 2009).
[13] P. Descouvemont, J. Phys. G 37, 64010 (2010); Theoretical Models for Nuclear Astrophysics, (Nova Science Publishers, 2003).
[14] JINA Reaclib, https://reaclib.jinaweb.orgSpeaker: Masahiko KATSUMA -
105
A new Multi-Channel and Monte Carlo R-Matrix analysis for the estimate of $\rm ^{17}$O destruction rate in stars
When stars approach the red giant branch, a deep convective envelope develops and the products of the CNO cycle appear at the stellar surface. In particular, the $\rm ^{17}O$ is enhanced in RGB and AGB stars. Spectroscopic analyses of O isotopic ratios of these stars provide a powerful tool to investigate the efficiency of deep mixing processes, such as those powered by convective overshoot, rotation, thermohaline instability, gravity wave and magnetic field. However, this method requires a precise knowledge of the reaction rates that determine the $\rm ^{17}O$ abundance in a H-burning shell, among which the $\rm ^{17}O(p,\gamma)^{18}F$ and the $\rm ^{17}O(p,\alpha)^{14}N$ reactions are the more relevant. Since the last release of rates compilations (see the JINA reaclib database, https://reaclib.jinaweb.org/) a number of experiments have updated reaction rates, incorporating new low-energy cross section measurements. In order to provide up-to-date input to the astrophysics community we performed simultaneous multi-channel and Monte Carlo R-Matrix analyses of the two reactions including all newly available data, resulting in realistic uncertainty ranges for the rates.
We will give an overview of the input data, the methodology, present the updated reaction rates and give an outlook on planned evaluations of other CNO-cycle reactions using the same approach.
Speaker: Prof. Andreas BEST (University of Naples "Federico II") -
106
Understanding the S- and C-type Giant Stars in the Milky Way
Asymptotic giant branch (AGB) stars are a key site of element synthesis in galaxies. As low-mass AGB stars evolve, they undergo internal helium-burning shell flashes, or thermal pulses. These thermal pulses temporarily extinguish the hydrogen-burning shell, allowing the convective envelope of the star to move into the intershell region, mixing products of helium-burning to the surface, including carbon. This is known as third dredge-up (TDU). The envelopes of the majority of AGB stars are oxygen-rich, and are classified as M-type. After enough mixing episodes, the star may eventually become “carbon-rich”, meaning the surface carbon-to-oxygen ratio (C/O) exceeds unity. These stars also show signs of s-process element enhancement, such as technetium. Generally, it is thought that the carbon enrichment follows a sequence from M-type to C-type (carbon-rich), moving through S-type (C/O = 0.5-0.99) before becoming C-type (C/O > 1). These intermediate S-type stars are of particular interest because they have likely only recently commenced episodes of TDU. A significant uncertainty in stellar modelling is the minimum stellar mass for TDU, as well as its efficiency as a function of stellar mass; therefore, accurately determining the masses of these S-stars can help us address these uncertainties.
The third data release of the Gaia survey has improved the luminosity determination of S-stars. However, constraining their current and initial masses remains complicated and requires stellar modelling, as AGB stars show long-period variability from radial pulsations, as well as longer term variability from thermal pulses. In this poster, we use radial pulsations to improve upon stellar mass estimates for Galactic S-stars. These will allow us to better constrain the minimum mass required for TDU in stellar models, and ultimately address uncertainties in the stellar yields of AGB stars and the chemical enrichment of the Milky Way galaxy.Speaker: Yoshiya MORI (Monash University) -
107
Astrophysical S factor of $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$ in the cluster effective field theory
The radiative proton capture reaction of $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$ is one of the thermonuclear reactions in the carbon-nitrogen-oxygen (CNO) cycle. This process provides a link between the type-I (CN) cycle and type-II (NO) cycle so that the $^{16}\mathrm{O}$ nucleus can be produced and the further types of the cycle start. We investigated the $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$ reaction in the effective field theoretical approach. The effective Lagrangian which is appropriate for this reaction in a stellar environment is introduced, and the capture amplitude and the corresponding S factor are calculated. In this work, we included two resonances due to the excited states of $^{16}\mathrm{O}$ as di-field propagators. By fitting our theoretical result to the empirical data of the S factor we determined the model parameters such as the low-energy constants and the S factor values of $S(0)=29.8-34.1~\mathrm{keV\ b}$ from the recent data sets are estimated. These results are compared to the estimations from several approaches such as the R-matrix and the potential models.
Speaker: Sangyeong SON (Kyungpook National University) -
108
The first direct measurement of the $65\,keV$ resonance strength of the $^{17}\mathrm{O}(p,\gamma)^{18}\mathrm{F}$ reaction at LUNA
The $^{17}\mathrm{O}(p,\gamma)^{18}\mathrm{F}$ reaction plays a crucial role in Hydrogen burning via CNO cycle. In particular at temperatures of interest for HBB in AGB stars ($20\,\mathrm{MK}<\mathrm{T}<80\,\mathrm{MK}$) the main contribution to the astrophysical reaction rate comes from the poorly constrained $E_R = 65\,\mathrm{keV}$ resonance. The strength of this resonance has only been determined through indirect measurements. The LUNA (Laboratory for Underground Nuclear Astrophysics) developed a new high sensitivity setup to measure this resonance directly.
The new setup is located at LNGS, where the cosmic ray background is reduced by several orders of magnitude. The residual background was further reduced by installing a devoted shielding made of $10$ cm lead and $4$ cm borated polyethylene. A $4\pi$ BGO detector was coupled with a target chamber and target holder of Aluminum, to increase the efficiency. The beam induced background contribution was precisely determined by collecting more than $300\,\mathrm{C}$ on $\mathrm{Ta}_2(^{18}\mathrm{O})_5$ targets.
With more than $400\,\mathrm{C}$ accumulated on $\mathrm{Ta}_2(^{17}\mathrm{O})_5$ targets the LUNA collaboration has performed the first direct measurement of the $65\,\mathrm{keV}$ resonance strength: this is the weakest resonance ever directly measured. In this contribution the improved experimental setup, the analysis procedure and preliminary results will be presented.
Speaker: Riccardo Maria GESUÈ (Gran Sasso Science Institute) -
109
First study of the $^{139}$Ba(n,γ)$^{140}$Ba reaction to constrain the conditions for the astrophysical i process
In recent years the plethora of new astronomical observations has shown that the synthesis of heavy elements cannot be explained just by the three traditional processes (s, r, and p). For this reason, new processes have been proposed that are able to explain these new observations. The ``intermediate'' or i process (see e.g. [1]) is one such process and corresponds to neutron densities and time scales intermediate between the slow (s) and the rapid (r) neutron-capture processes. It involves nuclei that are roughly 5 neutrons away from the last stable isotope and as such the majority of their nuclear properties are experimentally known. The only missing piece of information from the nuclear physics side is the neutron-capture reaction rates.
In the present work we investigate the production of La. La is one of the elements for which a large number of stellar observation data is available. La/Eu has been used traditionally to distinguish between the s and r processes, while enhanced Ba/La has been observed in metal-poor stars beyond s and r process values. At the considered neutron density of the i process, the uncertainties are dominated by the reaction $^{139}$Ba(n,γ)$^{140}$Ba.
In a collaboration between Michigan State University (MSU), the University of Cologne, the University of Guelph, the University of Oslo, iThemba LABS and Lawrence Livermore National Lab we have experimentally constrained the neutron capture rate for the $^{139}$Ba(n,γ)$^{140}$Ba reaction rate, for the first time [2]. The measurement of the relevant reaction took place at the CARIBU facility at Argonne National Lab. A combination of the $\beta$-Oslo method and the newly developed "Shape method" [3] were used to extract the nuclear level density and the $\gamma$ ray strength function, which were used to constrain the neutron capture reaction rate on $^{139}$Ba. The resulting rate is used in astrophysical i-process calculations which show that the uncertainty in the predictions for the double abundance ratio of [La/Eu] and [Ba/La] is greatly reduced and is now comparable to the uncertainties from astronomical observations. With this result we have been able to narrow down the group of stars out of the JINAbase that most likely have experienced neutron densities associated with rapidly accreting white dwarf simulations, which will be a stepping stone for further investigations of this astrophysical site.
[1] P. Denissenkov et al., ApJ Letters 834, L10 (2017)
[2] A. Spyrou, D. Muecher et al., under review at Physical Review Letters, 2023
[3] D. Muecher, A Spyrou et al., Phys. Rev. C 107, L011602, 2023Speaker: Dennis MUECHER (University of Cologne) -
110
Constraining neutron-capture cross section for the i-process for the 151−153Nd(n,γ)152−154Nd reaction via the β Oslo
Nucleosynthesis of heavy elements has been traditionally attributed to two neutron-capture processes, namely the s and r processes. Recent astronomical observations have revealed stars where the abundance distributions cannot be described by the aforementioned processes and for this reason the astrophysical i process was introduced (i for intermediate between s and r). While we know neutron densities are between the s and r process, the stellar site where it can occur has not yet been clearly identified and that is largely because of the nuclear uncertainties. The i process flow involves isotopes only a few steps from stability, and in this region the main nuclear physics uncertainty comes from neutron-capture reaction rates. Specifically neutron-capture reactions on Nd isotopes have been identified as important for the production of Eu and Sm. With this goal in mind, an experiment was run at the ATLAS facility using the low-energy beams delivered from CARIBU to constrain neutron-capture reactions of importance for the i process. $\beta$-decays and their corresponding $\gamma$-rays were identified using the SuN detector and the SuNTAN moving tape system. The $\beta$-decay of $^{152-154}$Pr into $^{152-154}$Nd was measured and the $\beta$-Oslo method was used to extract the nuclear level density and $\gamma$-ray strength function of $^{152-154}$Nd; preliminary results from this experiment will be presented here. From these statistical properties, $^{151-153}$Nd(n,$\gamma$)$^{152-154}$Nd reaction cross sections and reaction rates will be constrained and their significance to the i process will be presented.
Speaker: Hannah BERG (Michigan State University) -
111
Experimental integral cross-sections of photonuclear reactions on proton-rich $^{113}In$ and $^{114}Sn$ nuclei for cosmic nucleosynthesis modelling
Photonuclear reactions play an essential role in nucleosynthesis taking place in all sites, e.g., stars, novae, and interstellar gas media. Especially important these reactions are for formation of isotopes heavier than iron. The proton-rich p-nuclei, such as $^{114}Sn$, and $^{113}In$, can be created only via a complex sequence of radiative processes, involving both emission and capture of $\gamma$-rays [1]. Correct modelling of cosmic nucleosynthesis processes requires a wealth of confident experimental data both about nuclear reactions, and nuclear structure of involved nuclei.
Presented work is a continuation of our earlier studies of photonuclear reactions involving p-nuclei [2]. Yields of the $^{114}Sn(\gamma,n)^{113}Sn$ photonuclear reaction were measured in the bremsstrahlung energy range from 11.5 to 14 MeV with a step of 0.5 MeV using Linear Electron Accelerator of the National Science Centre "Kharkiv Institute of Physics and Technology" (Ukraine). For $^{113}In(\gamma,\gamma')^{113}In$ and $^{113}In(\gamma,n)^{112}In$ photonuclear reactions in the bremsstrahlung energy range from 7 to 23 MeV with a step of 2 MeV, the experiment was carried out using Microtron M-25 of the Institute of Nuclear Physics (Czech Republic). High-resolution gamma spectrometers based on HPGe detectors were used to measure induced activities in both experiments.
The results of experimental measurements are compared with the data available in the literature and with the nuclear reaction statistical model calculations obtained using TALYS 1.95 [3] computer codes.References
1. M. Arnoud, S. Goriely. The p-process of stellar nucleosynthesis: astrophysics and nuclear physics status. Phys.Rep. 384 (2003), p.1.
2. A.V. Chekhovska, et al. Stellar Nucleosynthesis: Experimental Yields of the $^{112}Sn(\gamma,n)^{111}Sn$ and $^{112}Sn(\gamma,p)^{111m,g}In$ Reactions for p-Nuclei Production Simulation. In “Nuclei in the Cosmos XV”, Eds. A.Formicola et al. Springer, (2019), p.301.
3. A. J. Koning, S. Hilaire and M. C. Duijvestijn. TALYS-1.0. Proc. of the Int. Conf. on Nuclear Data for Science and Technology. Nice: EDP Sciences, (2008), p.211.Speaker: Mrs Anastasiia CHEKHOVSKA (Institute of Solid State Physics, University of Latvia) -
112
Impact of the excited- and bound-state $\beta$-decays of $^{63}$Ni on weak $\textit{s}$-process nucleosynthesis [1]
Although about 90$\%$ and 50$\%$ of the solar-system Cu and Zn abundances are presumed to originate from the slow neutron-capture process (weak $\textit{s}$-process) during core He and shell C burning in massive stars, their stellar conditions are still poor known. This is because $^{63}$Ni (t$_{1/2}$=101.2$\pm$1.5yr) takes the key as a bottleneck for the synthesis of these nuclei in the $\textit{s}$-process branching: At high temperature, the $\beta$-decays from the excited states make a remarkable contribution. On the other hand, at low temperature and high density, the bound-state $\beta$-decays are important for highly ionized atoms when the transition energy is small. For these reasons many shell model calculations using different Hamiltonians were devoted to calculate excited-state $\beta$-decays, and both excited- and bound-state $\beta$-decay effects were studied in gross theory [2]. The calculated half-lives are unfortunately different from one another. In order to assess the significance of these effects, we carry out, for the first time, the $\textit{s}$-process nucleosynthesis calculations using all nuclear models of $\beta$-decays in a 25$M_{\odot}$ star with solar metallicity [1].
Firstly, we study the competition between $^{63}$Ni($\beta^{-}\bar{\upsilon}$)$^{63}$Cu vs. $^{63}$Ni(n,$\gamma$)$^{64}$Ni by taking account of the both effects to clarify the main nuclear flow paths [1]. We find that $^{63}$Cu and $^{64}$Ni change by 7$\%$ in abundance, $^{64}$Zn changes by more than 20$\%$, $^{65}$Cu and $^{66-68}$Zn change by 6$\%$, and all the other stable nuclei A = 69 – 90 change systematically by 5$\%$ at the mass coordinate $M_{r}=2M_{\odot}$ before the onset of the core Si burning, which depends strongly on the nuclear models [2]. We, secondly, confirm that although the $\beta$-decay half-life of $^{63}$Ni$^{28+}$ changes by more than 35$\%$ at T = 0.3 GK due to the effect of bound-state $\beta$-decay, abundance change of stable nuclei proves to be less than 3$\%$ [1]. These new quantitative results show the significance of future experimental measurement of the excited-state $\beta$-decays, in particular of $^{63}$Ni, and the microscopic nuclear model calculations of both excited-state and bound-state $\beta$-decays.[1] Xinxu Wang, B. Sun, D. Fang, Z. He, M. Kusakabe, T. Kajino, Z. Niu, et al. (2023), to be submitted.
[2] K. Takahashi, K. Yokoi, At. Data Nucl. Data Tables 36, 375 (1987).Speaker: Mr Xinxu WANG (Beihang University, China) -
113
Neutron capture and total cross-section measurements on 94,95,96Mo at n_TOF and GELINA
Cross-sections for neutron-induced interactions with molybdenum, in particular for the neutron capture reaction, play a significant role in various fields ranging from nuclear astrophysics to safety assessment of conventional nuclear power plants and the development of innovative technologies. Molybdenum is found in pre-solar silicon carbide (SiC) grains and an accurate knowledge of its neutron capture cross section has a crucial role in stellar nucleosynthesis models, in particular in Asymptotic Giant Branch (AGB) stars. From the work of Liu et al. [1], a deviation on the model predictions has been observed when using Mo cross section data from the two main KADoNiS versions [2][3], with KADoNiS 1.0 providing the better agreement with the grains data. This deviation is particularly evident when extrapolating the data to lower energies. A new measurement of the capture cross section of the molybdenum isotopes is therefore needed to confirm this trend at low thermal energy. In addition to its astrophysical role, molybdenum isotopes can be found as a fission product in fission power plants and the use of this material is under study for future improved reactors [4][5]. This shows the importance of an accurate knowledge of the total and capture cross-section for molybdenum isotopes.
Experimental data in the literature for the capture cross-section of Mo isotopes suffer from large uncertainties. This is also reflected in the large uncertainties of the cross-sections recommended in the ENDF/B-VIII.0 library [6]. Below 1 eV the relative uncertainty of the capture cross-section is above 18% for $^{94}$Mo and around 40% for $^{96}$Mo, while above 2 keV the uncertainties are in the order of 10-20% for $^{94,95,96}$Mo. The uncertainty on the capture cross section data in the libraires is also reflected in the uncertainty of the MACS (Maxwellian Averaged Cross Section) found in the latest version of KADoNiS [3], which presents uncertainties on the level of 10% in the MACS at 30 keV for all the molybdenum isotopes. One of the reasons for these large uncertainties is related to the absence of transmission data for enriched samples.
In this contribution the first transmission and radiative capture measurements results obtained at n_TOF (CERN, Switzerland) and GELINA (EC-JRC Geel, Belgium) will be presented. Moreover, the updated values of the MACS for $^{94,95,96}$Mo will be shown. The effect of these new preliminary values of the cross section in stellar nucleosynthesis calculations for AGB stars will be presented.
REFERENCES
[1] N. Liu, T. Stephan, S. Cristallo et al., Astrophysical Journal, 881, 28 (2019).
[2] Z.Y. Bao, et. Al., Atomic Data and Nuclear Data Tables 76, (2000).
[3] I. Dillmann, et al., Proceeding of the workshop EFNUDAT Fast Neutrons (2009).
[4] B. Cheng, Y.-J. Kim, P. Chou, Nuclear engineering and Technology, 48, 16-25 (2016).
[5] P. Herve et al., EPJ Nuclear Sciences & Technologies, 4, 49 (2018).
[6] D.A. Brown et al., Nuclear Data Sheets, 148, 1 (2018).Speaker: Riccardo MUCCIOLA (University and INFN Torino) -
114
Estimation of fission from proton-induced uranium-238 using the Langevin method
RAON aims to produce rare isotope beams through proton-induced fission of uranium-238. In this study, we utilize the Langevin method to predict the mass distribution by plotting trajectories based on the potential surface of compound nuclei, integrating the Liquid Drop Model (LDM) and the Shell model (SM). To enhance the shell effect at high excitation energy, we employ a multi-chance fission (MCF) approach. Our predictions provide valuable insights and bridge the gaps in experimental data, contributing to our understanding of isotope production.
Speaker: Mr Chang-hoon SONG (Pusan National University) -
115
Measurement of the 159Tb(n, γ) cross section at the CSNS Back-n facility
The stellar (n, γ) cross section data for the mass numbers around A ≈ 160 are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occurs in the thermally pulsing asymptotic giant branch (TP–AGB). The new measurement of (n, γ) cross sections for 159Tb was performed using the C6D6 detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source (CSNS) with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels are reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) are derived from the measured 159Tb (n, γ) cross sections at kT = 5 ~100 keV and are in good agreement with the recommended data of KADoNiS-v0.3 and JEFF-3.3, while KADoNiS-v1.0 and ENDF-VIII.0 significantly overestimate the present MACS up to 40% and 20%, respectively. A sensitive test of the s-process nucleosynthesis is also performed with the stellar evolution code MESA. Significant changes in abundances around A ≈ 160 are observed between the ENDF/B-VIII.0 and present measured rate of 159Tb(n, γ) 160Tb in the MESA simulation.
Speaker: Prof. Suyalatu ZHANG (Inner Mongolia Minzu University) -
116
Production of solar abundances for nuclei beyond Sr: do we need better nuclear physics input?
It is widely accepted that the slow (s-process) and rapid (r-process) scenarios of neutron captures contribute to the solar abundances of trans-Fe nuclei.
The yields of up-to-date and totally independent models for s- and r-process show a general good and complementary agreement in reproducing the Solar System abundances. However, some local discrepancies do occur and this fact could hint to a contribution by another nucleosynthesis mechanisms (e.g. the i-process) as well as the need for more precise nuclear physics inputs to be used for the nucleosynthesis calculations. In particular in last years the need for new (theoretical and hopefully experimental) estimates for the beta decay rates in stellar plasma conditions of some key isotopes has been highlighted. We present an analysis of the s-process contributions to Sr–Pr region from recent models of
asymptotic giant branch stars, for which uncertainties are known to be dominated by nuclear effects.
In particular, we will focus on for four nuclei (98Mo, 106Pd, 118Sn, and 135Ba) whose predicted abundances are in clear disagreement with observed ones and whose s-process yields will be crucially modified if the half-lives of some isotopes (i.e. 113,115Cd, 115In, and 134,135Cs) would be different in ionized plasma environments.Speaker: Sara PALMERINI (University of Perugia and INFN Perugia, Italy) -
117
Measurement of the 27Al(p,alpha)24Mg fusion reaction at astrophysical energies via the Trojan Horse Method.
The abundance of 26Al carries a special role in astrophysics, since it probes active nucleosynthesis in the MilkyWay and constrains the Galactic core-collapse supernovae rate. It is estimated through
the detection of the 1809 keV-line and from the superabundance of 26Mg in comparison with the most abundant Mg isotope (A=24) in meteorites. For this reason, high precision is necessary also in the investigation of the stable 27Al and 24Mg [1,2]. Moreover, these nuclei enter the so-called MgAl cycle playing an important role in the production of Al and Mg [3]. Recently, high-resolution stellar surveys have shown that the Mg-Al anti-correlation in red-giant stars in globular clusters
may hide the existence of multiple stellar populations, and that the relative abundances of Mg isotopes may not be correlated with Al.
The common thread running through these astrophysical scenarios is the 27Al(p,alpha)24Mg fusion reaction, which is the main 27Al destruction channel and directly correlates its abundance with the 24Mg one. Since available spectroscopic data and tabulated reaction rates show large uncertainties owing to the vanishingly small cross section at astrophysical energies, we have applied the Trojan Horse Method (THM) to the three-body quasi-free reaction d(27Al,alpha 24Mg)n.This has allowed us to perform high precision spectroscopy on the compound nucleus 28Si, from which we extracted important information on the 27Al(p,alpha)24Mg fusion cross section in the energy region of interest
for astrophysics, not accessible to direct measurements. All details can be found in refs.[4,5]. In particular, the indirect measurement made it possible to assess the contribution of the 84 keV
resonance and to lower upper limits on the strength of nearby resonances.
We have evaluated the effect of the THM recommended rate on
intermediate-mass asymptotic giant branch stars experiencing hot bottom burning. Here, a sizeable increase in surface aluminum abundance is observed at the lowest masses due to the modification on the fusion cross section, while 24Mg is essentially unaffected by the change we determined.[1] S. Palmerini et al., Monthly Notices of the Royal Astronomical Society 467, 1193 (2017).
[2] C. Iliadis et al., The Astrophysical Journal Supplement 193, 23 (2011).
[3] C. Iliadis et al., Nuclear Physics A 841, 3 (2010).
[4] M. La Cognata et al., The Astrophysical Journal 941, 96 (2022).
[5] M. La Cognata et al., Physics Letters B 826, 136917 (2022).Speaker: Sara PALMERINI (University of Perugia and INFN Perugia, Italy) -
118
The impact of systematic and statistical nuclear uncertainties on the i-process nucleosynthesis
The observed surface abundance distribution of Carbon-enhanced metal-poor (CEMP) r/s-stars suggests that these stars have been polluted by an intermediate neutron-capture process (the so-called i-process) occurring at intermediate neutron densities between the r- and s-processes. Triggered by the ingestion of protons inside a convective He-burning zone, the i-process could be hosted in several sites, a promising one being the early AGB phase of low-mass low-metallicity stars. The i-process remains however affected by many uncertainties including those of nuclear origin since it involves hundreds of nuclei for which reaction rates have not yet been determined experimentally.
We investigate both the systematic and statistical uncertainties associated with theoretical nuclear reaction rates of relevance during the i-process and explore their impact on the i-process elemental production, and subsequently on the surface enrichment, for low-mass low-metallicity stars during the early AGB phase.
We use the TALYS reaction code (Koning et al. 2023) to estimate both the model and parameter uncertainties affecting the photon strength function and the nuclear level densities, hence the radiative neutron capture rates. The impact of correlated systematic uncertainties is estimated by considering different nuclear models, as detailed in Goriely et al. (2022). In contrast, the uncorrelated uncertainties associated with local variation of model parameters are estimated using a variant of the backward-forward Monte Carlo method to constrain the parameter changes to experimentally known cross sections before propagating them consistently to the neutron capture rates of nuclei of i-process interest.
On such a basis, the STAREVOL code (Siess et al. 2006) is used to determine the impact of nuclear uncertainties on the i-process nucleosynthesis in a 1 M$_{\odot}$ [Fe/H] = - 2.5 model star during the proton ingestion event in the early AGB phase. A large nuclear network of 1160 species coherently coupled to the transport processes is solved to follow the i-process nucleosynthesis.We show the importance of both statistical and systematic uncertainties with respect to the surface abundances in AGB stars and we identify and provide a list of reaction rates that would need to be better constrained in the future in order to improve our understanding of the i-process.
Speaker: Sébastien MARTINET (Université Libre de Bruxelles) -
119
Massive star models with the updated 12C+12C reaction rate
The reaction rate of the carbon fusion reaction is one of the basic inputs in the stellar model to understand the final stages of the massive star evolution. However, this reaction rate is yet uncertain because it depends on the extrapolation methods. The cross-section measurement for this reaction is challenging because the energy range relevant to the stellar evolution is much below the Coulomb barrier, i.e., the Gamow window is only 1.5-2.5 MeV. In this study, we update the carbon fusion reaction rate by obtaining new extrapolation results based on the measurement data available in the literature to date. By adopting our new reaction rate, we calculate massive star models with the 1D stellar evolution code, MESA (Modules for Experiments for Stellar Astrophysics). We find that our updated nuclear reaction rate is about a half of the previous one (Caughlan and Fowler 1988), resulting in almost negligible changes in the HR-diagram of the massive star models in consideration. However, the updated rate has a significant impact on the temperature change in the core and thus on the neutrino cooling during the carbon burning stage. We find that our updated reaction rate reduces the lifetime of the carbon burning stage by a factor of ~ 0.7.
Speaker: Gwangeon SEONG (UNIST) -
120
The COREA experiment: measurement of 12C(α,𝛄)16O reactions with an active-target TPC
The COREA (Carbon Oxygen Reaction Experiment with Active-target TPC) is an experiment to measure the precise cross-section of the 12C(α,𝛄)16O reaction in stellar nucleosynthesis. The reaction rate of 12C(α,𝛄)16O determines the 12C/16O abundance ratio in the universe and the entire scenario of the stellar nucleosynthesis after the helium burning up to the Fe core in the last years of stellar life. We are developing a novel detector system consisting of an active-target time projection chamber in a conduction-cooled superconducting magnet of the magnetic field up to 3 T and a LaBr3 gamma detector array. In this talk, we will present the status of the experiment and the development of the unique COREA detector system.
Speaker: Shin Hyung KIM (Korea University)
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103
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Poster session (Radioactivity and meteorites)
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Poster session (Stellar modelling)
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121
Full 3D Fluid Simulations of the Convective Urca Process in a Simmering White Dwarf Star
Type Ia supernovae are extremely bright thermonuclear events and have been very well studied by numerous observations. However, there remain many open questions about the progenitor system for these explosive events. In the single-degenerate progenitor model, in which a white dwarf accretes mass from a stellar companion, a phase of simmering occurs where carbon burning drives core convection prior to the thermonuclear explosion. A poorly understood aspect of this simmering phase is the convective Urca process, a linking of convection and weak nuclear reactions. We present full 3D fluid simulations of the A=23 convective Urca process in a simmering white dwarf using the MAESTROeX low-Mach hydrodynamic software. This enables us to model both the slow moving convection and weak nuclear reactions. We characterize the extent of mixing across the Urca shell, the convective velocity, and the energy losses due to neutrino emissions. These results can inform 1D stellar evolution models which track the longer timescale evolution of the carbon simmering phase. This research was supported in part by the US Department of Energy (DOE) under grant DE-FG02-87ER40317.
Speaker: Brendan BOYD (Stony Brook University)
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121
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Poster session (The early Universe, galactic evolution)
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122
Heavy Element Nucleosynthesis and Galactic Chemical Evolution
The origin and evolution of heavy elements in nature are not yet fully understood. THis talk will overview the current status of models for both the formation of both r-process and nu-p-process elements. We summarize recent state-of the art developments of supernova and binary neutron star evolution in the context of both the r-process and p-process nucleosynthesis. In particular, we highlight two recent recent works detailing the emerging evidence for the important role of hypernovae (energetic supernovae) and collapsars (jets from the collapse of massive stars to a black hole). These studies illuminate how such events may play a key role in the origin and early evolution of explosive heavy-element nucleosynthesis.
Speaker: Grant MATHEWS (University of Notre Dame) -
123
An exact solution of the higher-order gravity in standard radiation-dominated era
We report that the standard evolution of radiation-dominated era (RDE) universe $a \propto t^{1/2}$ is a sufficient condition for solving a sixth order gravitational field equation derived from the Lagrangian containing $B R^{ab}R_{ab} + C R R^{;c}_{\phantom{;c}c}$ as well as a polynomial $f(R)$ for a spatially flat radiation FLRW universe. By virtue of the similarity between $R^{ab}R_{ab}$ and $R^2$ models up to the background order and of the vanishing property of $R^{;c}_{\phantom{;c}c}$ for $H=1/(2t)$, the analytical solution can be obtained from a special case to general one. This proves that the standard cosmic evolution is valid even within modified gravitational theory involving higher-order terms. An application of this background solution to the tensor-type perturbation reduces the complicated equation to the standard second order equation of gravitational wave. We discuss the possible ways to discriminate the modified gravity model on the observations such as the gravitational wave from the disturbed universe and primordial abundances.
Speaker: Chae-min YUN (Soongsil University) -
124
New targets for relic antineutrino capture
$^{163}$Ho has been considered as a suitable candidate for the capture of relic antineutrinos. However, the detection of the relic antineutrino using $^{163}$Ho is extremely challenging with current techniques. Therefore, we have searched for new targets for relic antineutrino detections through the resonant capture on nuclides undergoing electron capture. We have investigated nuclear and atomic properties of all nuclides. And we finally propose $^{131}$Ba, $^{159}$Dy, $^{175}$Hf, $^{195}$Au, and $^{243}$Cm as new candidates for the relic antineutrino detection, and call for high precise experiments of $Q_{\rm EC}$-values and intensities of EC decays for these new candidates.
Speaker: Dr Jeong-Yeon LEE (Soongsil University) -
125
Measurement and evaluation of the 7Be + n reactions approaching the cosmological lithium problem
The cosmological lithium problem has been known as the outstanding discrepancy of primordial lithium abundances between observations and theoretical predictions. We have measured key nuclear reactions which act to reduce $^7$Li during the big bang nucleosynthesis (BBN), namely, $^7$Be$(n,p)^7$Li and $^7$Be$(n,α)^4$He, by means of the Trojan Horse method [1].
We also performed $R$-matrix fits to data sets including both the previous and present cross sections of the $(n,p_0)$, $(n,p_1)$ and $(n,\alpha)$ reaction channels based on the resonances at known excited levels. This analysis resulted in an improved uncertainty evaluation of the $(n,p_0)$ cross section, and the first-ever quantification of the $(n,p_1)$ contribution in the BBN energy region.
We implemented the revised total reaction rate summing both the $(n,p_0)$ and $(n,p_1)$ contributions in one of the state-of-the-art BBN codes PRIMAT. It results in a reduction of the predicted $^7$Li abundance by about one tenth, which would offer less nuclear physics uncertainty to further theoretical works on the cosmological lithium problem.
[1] S. Hayakawa et al., Astrophys. J. Lett., 915, (2021), L13.
Speaker: Seiya HAYAKAWA (Center for Nulear Study, University of Tokyo) -
126
Big Bang Nucleosynthesis in the Extended Starobinsky Model and Early Universe Chemistry
Our study links cosmic evolutions in the extended Starobinsky model (eSM), Big Bang Nucleosynthesis (BBN), and early universe chemistry. We demonstrate standard and oscillating cosmic evolutions and discuss BBN constraints. By connecting BBN abundances to the early universe chemistry, we identify the formation of intriguing and critical molecular structures. These findings underscore the pivotal role that early universe chemistry plays in shaping our understanding of cosmological phenomena.
Speaker: Jubin PARK (Soongsil University and OMEG institute) -
127
Searching for a cosmological variation of the gravitational constant using strong gravitational fields
Searching for varying dimensionless physical constants presents a meaningful characteristic in experimental and observational studies. One of the most valuable explorations of these variations could depend on the evolution of white dwarf stars. Applying the spectrum of white dwarf star: G191-B2B, we derive a robust limit on the cosmological variation of the gravitational constant G˙/G=(0.238±2.959)×10−15yr−1. This limit proposes a potential test of the framework of modern unification theories.
Speaker: Duc Thong LE (Institute for Computational Science) -
128
Chemical Abundance Patterns of Very Metal-Poor Stars Dynamically Associated with Substructures in the Milky Way
We present a detailed chemical abundance analysis for about 40 Very Metal-Poor (VMP; [Fe/H] < -2.0), selected from Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) surveys. Their high-resolution (R ~ 45,000) spectra were obtained with GEMINI/GRACES, and their atmospheric stellar parameters and various chemical abundance ratios were derived. Because most of them are associated with the well-known Milky Way (MW) substructures, such as the Gaia-Sausage-Enceladus, Thamnos, and others, we investigate their dynamical characteristics and chemical abundance patterns to characterize their progenitor dwarf galaxies. Their chemodynamical properties will provide valuable clues to infer their accretion history as well as the assembly history of the MW.
Speaker: MIJI JEONG (Chungnam National University) -
129
Astrophysically relevant Neutron induced reactions studied via THM
Neutron induced reactions on unstable nuclei play a significant role in the nucleosynthesis of the elements in the cosmos. Their interest range from the primordial processes occurred during the Big Bang Nucleosynthesis up to the “stellar cauldrons” where neutron capture reactions build up heavy elements. In the last years, several efforts have been made to investigate the possibility of applying the Trojan Horse Method (THM) to neutron induced reactions mostly by using deuteron as “TH-nucleus”. Here, the main advantages of using THM will be given together with a more focused discussion on the 7Be(n,alpha)4He “study case” and the 14N(n,p)14C reaction. The former reaction was studied via the THM application to the quasi-free 2H(7Be,aa)p reaction and it represents the extension of the method to neutron-induced reactions in which an unstable beam is present. The 14N(n,p)14C reaction was studied via the 2H(14N,p14C)p experiment performed at INFN-LNS via a 50 MeV 14N beam provided by the INFN-LNS TANDEM accelerator. Preliminary results shows the population of intermediate 15N excited states at astrophysical energies. These applications open new frontiers in the application of the method (i.e. the study of 7Be+d or 11C+alpha reactions) extending its range of applicability for contributing to astrophysically relevant problems.
Speaker: Dr LIVIO LAMIA (UniCT & INFN-LNS)
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122
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Poster session (The s-process)
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Poster session (Underground nuclear astrophysics)
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130
Nuclear reactions of astrophysical interest on neon isotopes at LUNA
A group of reactions involving neon isotopes have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) using the intense proton beam delivered by the LUNA 400 kV accelerator and a windowless differential-pumping gas target.
For years the $\mathrm{^{22}Ne(p, \gamma)^{23}Na}$ reaction was the most uncertain reaction in the NeNa cycle of hydrogen burning. LUNA was able to discover three new low-energy resonances in this reaction and to measure the nonresonant capture to unprecedently small energy. LUNA has significantly reduced the uncertainty surrounding this reaction and the NeNa cycle, but there is now a need for new, precise data on other reactions in the NeNa cycle.
The $\mathrm{^{20}Ne(p, \gamma)^{21}Na}$ reaction is the slowest in the NeNa cycle and determines the overall rate at which the entire cycle proceeds. Within the temperature range of 0.1 GK to 1 GK, the rate of the reaction is primarily influenced by the 366 keV resonance and the direct capture component. These factors play a crucial role in determining the quantity of $\mathrm{^{22}Na}$ produced, which is a key observable in gamma-ray astronomy. LUNA reduced the uncertainty on the 366 keV resonance strength from 18% to 7% and for the first time measured the direct capture below 370 keV.
New measurements of low energy resonances in the $\mathrm{^{21}Ne(p,g)^{22}Na}$, the second reaction in the NeNa cycle, are ongoing.
Furthermore, new studies are dedicated to $\mathrm{^{22}Ne}$, an important neutron source in the weak s-process via the $\mathrm{^{22}Ne(\alpha,n)^{25}Mg}$ reaction.
The $\mathrm{^{22}Ne(\alpha,\gamma)^{26}Mg}$ reaction, which competes with the $\mathrm{^{22}Ne(\alpha,n)^{25}Mg}$ reaction has been recently studied. At temperatures T < 300 MK the $(\alpha,\gamma)$ channel becomes dominant and the rate of the $\mathrm{^{22}Ne(\alpha,\gamma)^{26}Mg}$ reaction is influenced by multiple resonances that have been solely investigated using indirect techniques thus far. The new upper limits determined by LUNA cause the intershell $\mathrm{^{25}Mg/^{26}Mg}$ ratio to decrease by a factor of 15 in 5 $M_{\odot}$ AGB stars.
Recent results will be presented and discussed, together with future perspectives for the study of the $\mathrm{^{22}Ne(\alpha,n)^{25}Mg}$ reaction.Speaker: Federico FERRARO (INFN - LNGS)
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130
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New facilities, instruments and tools
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131
Astrophysics program at Yemilab
IBS has recently constructed a new underground laboratory, Yemilab, in Korea. It is 1000 meters underground and spacious with more than 3000 m^2 experimental area. The Center for Underground Physics has developed programs for weakly interacting dark matter searches with scintillators and low-temperature detectors. We also have plans to search the rare nuclear decays, such as neutrinoless double beta decays, 180mTa decays, etc. I will describe the current status of the research and address a few issues related to nuclear physics.
Speaker: Yeongduk KIM (Institute for Basic Science) -
132
Nuclear Astrophysics at the Notre Dame Nuclear Science Lab
There is a distinguished history of nuclear astrophysics research at the Notre Dame Nuclear Science Lab (NSL). This has been fostered by University investment and strong support from the National Science Foundation. The NSL provides the research base for some 20 Notre Dame faculty members and approximately 35 graduate students as well as supporting the research programs of a number of external users. The laboratory hosts a number of unique facilities and instruments that help facilitate astrophysical research such as the St. George recoil separator coupled to the high-intensity 5U accelerator, the worlds-only triple solenoid in-flight radioactive beam facility, and one of only three operating Enge split-pole spectrometers in the U.S. The NSL maintains three on-site accelerators, which can operate simultaneously and continuously as well as the only underground nuclear accelerator in the U.S. at the SURF facility in South Dakota. The current research program at the NSL will be presented along with plans for future instrument upgrades and additions.
Research supported by the National Science Foundation grant NSF PHY-2011890 and the University of Notre Dame.
Speaker: Dan BARDAYAN (University of Notre Dame) -
133
Nuclear Astrophysics with low-energy RI beams at CRIB
Astrophysical reactions involving radioactive isotopes (RI) often play an important role
in explosive stellar environments. Although the RI are seldom seen on the earth due to
the finite lifetime, they do exist in stars, and contribute to the evolution and thermal
dynamics of stellar objects. Experimental efforts have been made for the studies on such
RI-involving reactions.CRIB (CNS Radioisotope Beam Separator) is a low-energy RI beam separator
operated by Center for Nuclear Study, the University of Tokyo, located at the RI beam factory (RIBF) of RIKEN Nishina Center.
Various experimental projects based on interests for nuclear astrophysics have been
carried out at CRIB, forming international collaborations.
The present status of CRIB, including the new developments for the RI beams, is reported.
Recent projects of astrophysical reaction studies with RI beams at CRIB are also discussed;1) Trojan Horse Method measurement for the 7Be+n reactions which may affect the
7Be abundance in the Big-Bang nucleosynthesis, to find
a solution for the cosmological 7Li abundance problem.2) Resonant scattering measurement for the 22Mg(alpha, p) reaction, which affects the light curve of X-ray bursts.
3) Direct measurement of the 26Si(alpha, p) reaction, another relevant RI reaction in X-ray bursts.
Speaker: Hidetoshi YAMAGUCHI (Center for Nuclear Study, the University of Tokyo) -
134
Recent astrophysics results from the Enge Split-pole Spectrograph Program at the Triangle Universities Nuclear Laboratory
The Triangle Universities Nuclear Laboratory (TUNL) is home to one of the only functioning magnetic Enge split-pole spectrographs in North America. The spectrograph was recommissioned in 2017 and has been used to perform a suite of experiments aimed at constraining nucleosynthesis in stars. An overview will be presented of the successful experiments and results that have been performed at the facility in the last 5 years. These include constraining the 18F(p,a)15O reaction, a key reaction in understanding gamma-ray signals from classical novae; measurements of states important for the 17O(a,n)20Ne which strongly affects the s-process efficiency in rotating massive stars; and determining the spin-parities of resonances in the 39K(p,g)40Ca reaction, reducing its reaction rate uncertainty by over factor of 10. The high resolution of the spectrograph coupled with a dedicated high-precision beamline at TUNL enables us to differentiate closely-spaced energy levels astrophysics that are currently impossible in inverse kinematics. A modern statistical analysis pipeline will also be showcased, which helps drive particle transfer reaction measurement analysis for astrophysics into a new era.
Speaker: Thanassis PSALTIS (NCSU/TUNL) -
135
Improved measurements of ($\alpha,p$) reactions with a new ANASEN design
Several ($\alpha,p$) reactions on proton-rich nuclei are among the most important nuclear reactions occurring during Type I X-ray bursts. However, large uncertainties remain in these reaction rates due to the lack of direct measurements. The Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) is a gas target and charged particle detector designed for studying ($\alpha,p$) reactions. A previous $^{18}$Ne($\alpha,p$)$^{21}$Na measurement with ANASEN used a position-sensitive proportional counter along the beam axis with a barrel of thick silicon detectors far from the beam axis to track protons from these reactions [1]. Due to the poor tracking resolution of the proportional counter, this measurement achieved a center-of-mass energy resolution of only 1.4 MeV. We have developed a new approach, replacing the proportional counter with a hexagonal barrel of thin (~80 $\mu$m) silicon detectors. This allows pure helium gas to be used and improves the tracking resolution, though at a cost of overall efficiency. The new setup was used in stable beam tests at the Fox Laboratory at Florida State University, and in both stable and radioactive beam measurements at TRIUMF-ISAC. Results from stable beam tests and from a measurement of the $^{18}$F($\alpha,p$)$^{21}$Ne excitation function, which may impact asymptotic giant branch nucleosynthesis [2] and helium burning on accreting white dwarfs [3], will be presented. Plans for future measurements at TRIUMF-ISAC and FRIB will be discussed.
Funding Acknowledgement: This material is based upon work supported by NSF Grant No. PHY-2012522, US DOE Grant No. DE-FG02-96ER40978, and the National Science Foundation Graduate Research Fellowship Program under Grant No. GR-00010333.
[1] M. Anastasiou, I. Wiedenhöver, J.C. Blackmon, L.T. Baby, D.D. Caussyn, A.A. Hood, E. Koshchiy, J.C. Lighthall, K.T. Macon, J.J. Parker, T. Rauscher, and N. Rijal, Phys. Rev. C 105, 055806 (2022).
[2] A.I. Karakas, H.Y. Lee, M. Lugaro, J. Görres, and M. Wiescher, Astrophys. J. 676, 1254 (2008).
[3] K.J. Shen and L. Bildsten, Astrophys. J. 699, 1365 (2009).Speaker: Keilah DAVIS (Louisiana State University) -
136
Status of the RAON Facility
The construction of the RAON (Rare Isotope Accelerator complex for ON-line experiments) facility was launched in 2011 as the Rare Isotope Science Project (RISP). The RAON was designed to produce a variety of stable and rare isotope beams to be used for basic science research and applications. The RAON consists of a heavy ion superconducting linear accelerator (SCL2) as the driver for the In-flight Fragmentation (IF) system, a proton cyclotron as the driver for the ISOL (Isotope Separation On-Line) system, and a superconducting linac (SCL3) for the post-acceleration of ISOL beams. The ISOL and IF systems can be operated independently, while the rare isotopes produced by the ISOL system can be injected to the superconducting linac SCL3 and then to the SCL2 for further acceleration to produce even more exotic rare isotopes through a two-step method (ISOL+IF). This combined scheme (ISOLIF) for producing more exotic rare isotopes in sequence is the uniqueness of the RAON facility.
The first phase of the RISP, constructing the superconducting linear accelerator SCL3, cryo-plant systems, an ISOL system with a cyclotron, supporting facilities, buildings, and seven experimental systems is completed. The construction of the superconducting linac SCL2 to deliver a wide range of heavy ion beams, e.g. uranium beams of 200 MeV/u with a beam current of 8.3 pμA and proton beams of 600 MeV with 660 pμA will be done as the second phase.The first beam commissioning of the SCL3 was carried out successfully by accelerating the Argon beam through 22 QWR modules up to 2.47 MeV/u with 34 μA, and then through 32 HWR modules to accelerate Ar beams to 17.6 MeV/u with 21 μA. The accelerated Ar beams were delivered to the KoBRA (Korea Broad acceptance Recoil Spectrometer and Apparatus) system to produce rare isotopes.
Also, the ISOL system was commissioned by bombarding the SiC target with proton beams to generate radioactive isotopes such as Na and Al. The beam commissioning of other low energy experimental facilities such as the MMS (Mass Measurement System), CLS (Colinear Laser Spectroscopy), and NDPS (Nuclear Data Production System) will also be prepared soon. We will report on the current status of the RAON facility.
Speaker: Taeksu SHIN (IRIS, IBS)
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Poster session
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Group Photo and excursion preparations
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Excursions
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Core-collapse supernovae, mergers and the r-process
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139
The r-process and neutrinos in neutron star mergers
The merging of two neutron stars is a true multimessenger event that includes gravitational waves, an electromagnetic signal, and the emission of enormous numbers of neutrinos. In order to understand these signals we need a careful accounting of the microphysics that occurs during and after the merger. I will focus on the elements produced in these objects and the effect of two aspects of this microphysics; nuclear models/reactions and neutrino flavor transformation physics. In particular, I will discuss the importance of new developments in these areas to predictions of r-process observables and the astrophysical origin of the r-process.
Speaker: Gail MCLAUGHLIN (North Carolina State University) -
140
Binary Neutron Stars, Core Collapse Supernovae and the Nuclear Equation of State
The properties of nuclear matter at extremely high densities and temperatures remain a mystery. This talk discusses two environments for which the nuclear matter can be found at the highest densities. These are: during the collapse of the core of a massive star to form a supernova or black hole; and during the merger of two neutron stars to form a black hole. Here, we highlight recent progress by our group toward exploring the nuclear equation-of-state effects in these environments. In particular, we describe new insight into the explodability of supernova progenitors and a probe of the the non-perturbative regime of quark matter in the gravitational radiation emitted during binary neutron-star mergers.
Speaker: Grant MATHEWS (University of Notre Dame) -
141
Role of light-mass nuclear reactions in the r-process nucleosynthesis, revisited
We study the sensitivity of the r-process nucleosynthesis to the nuclear reactions of light nuclei.
We first update nuclear reaction data in Libnucnet code if available in experiments. We then calculate the r-process nucleosynthesis in the core-collapse supernovae and collapsar. For core-collapse supernovae we consider two different scenarios: the magnetohydrodynamic (MHD) jet model and a simple exponential model for the weak r-process.
We find important reactions such as 14C(n, gamma)15C to which the r-process is sensitive. We finally discuss reaction network flows under the various conditions.Speaker: Youngman KIM (CENS, IBS) -
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Chemical compositions of r-process enhanced metal-poor stars discovered by the LAMOST/Subaru telescopes
Metal-poor stars are thought to have the result of nucleosynthesis in the early stages of galaxy formation in their atmospheres. A variety of surveys and follow-up observations have been performed to determine detailed abundance patterns for many metal-poor stars. The r-process, which provides about a half of the elements heavier than iron, is thought to be caused by neutron star mergers. However, an r-process enhanced extremely metal-poor star ([Fe/H] $= -3.5$) has been discovered (Yong et al. 2021), which should be formed in the early stages of galaxy formation, suggesting that the r-process needs to occur with very short time scale through, for instance, special types of supernovae.
We have obtained chemical abundances by high-dispersion spectroscopic observations with Subaru/HDS for about 400 metal-poor stars estimated to be [Fe/H] $< -2$, which were discovered by the LAMOST spectroscopic survey (Aoki et al. 2022, Li et al. 2022). These observations have identified many r-process enhanced stars, of which the most metal-poor J1109+0754 ([Fe/H]$=-3.4$) and the brightest J0040+2729 ([Fe/H]$=-2.7$) were followed-up with long exposures with Subaru/HDS. The observations were conducted in the wavelength region around 4000A, where there are many absorption lines for neutron-capture elements including thorium, and for J0040+2729, observations were also conducted in the near-UV region up to around 3300A. We have obtained the abundances for many elements, including thorium, and upper limits for lead and uranium from the spectra. The overall abundance patterns of both stars exhibit a good agreement with the solar r-process pattern as found for r-process-enhanced stars previously studied, but some of the lighter elements show slight deviations from the solar r-process pattern. This result could indicate the diversity of the r-process. The abundance patterns of r-process elements in very metal-poor stars constrain the timing of neutron star mergers in the early stages of galaxy formation and models of supernova explosions.Speaker: Satoshi HONDA (University of Hyogo) -
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Optical properties of magneto-rotaional jet-driven supernovae associated with r-process nucleosynthesis
Magnetorotational-driven supernovae (MRNSe) are a peculiar type of core-collapse SNe. Their progenitors are fast-rotating massive stars with strong magnetic fields and they are candidates for the central engine of hypernovae and gamma-ray bursts. They are also expected to be astronomical sites for the r-process, as they have a different explosion mechanism from regular SNe. MRSNe may have very neutron-rich ejecta suitable for the r-process due to the strong effect of the jet-driven explosion. In studies of galactic chemical evolution, MRSNe are expected to be additional r-process sources because they have different frequencies and delay times from neutron-star mergers. Although some observations suggest jet-like SNe, the occurrence of r-process nucleosynthesis has never been directly confirmed. In this presentation, we focus on the effect of r-process nucleosynthesis in MRSNe on possible observational properties in SN light curves. The r-process occurring in the central region of the SN provide different opacity and heating sources compared to canonical core-collapse SNe. We quantitatively investigate the effects of r-process elements and ${}^{56}{\rm Ni}$ abundances on the light curves based on a series of radiative hydrodynamics simulations. We confirm that the influence of the r-process is not significant for all models, which is consistent with the fact that we have not still identified r-process elements in SNe. However, there are some models where the existence of r-process elements can be observationally confirmed by current high presicition obervations (e.g., JWST) and future telescopes.
Speaker: Dr Nobuya NISHIMURA (RIKEN)
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Coffee break
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High-density matter
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Building relativistic mean-field models for neutron stars in light of the PREX-2 and CREX results
We construct new effective interactions using the relativistic mean-field model with the isoscalar- and isovector-meson mixing. Taking into account the results of neutron skin thickness of $^{208}$Pb and $^{48}$Ca by the PREX-2 and CREX experiments as well as the particle flow data in heavy-ion collisions, the observed mass of PSR J0740+6620, and the tidal deformability of a neutron star from binary merger events, we study the ground-state properties of finite nuclei and the characteristics of nuclear matter and neutron stars. It is found that the $\sigma$-$\delta$ mixing is very important to understand the terrestrial experiments and astrophysical observations of neutron stars self-consistently. Especially, we present that the equation of state for neutron stars exhibits the rapid stiffening around twice the nuclear saturation density, which is caused by the soft nuclear symmetry energy due to the $\sigma$-$\delta$ mixing. It is also noticeable that the small dimensionless tidal deformability of a canonical neutron star observed from GW170817 can be explained within the current relativistic mean-field models.
Speaker: Dr Tsuyoshi MIYATSU (Soongsil University) -
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Supernova equation of state and neutrino-nucleon reaction rates based on bare nuclear forces
The equation of state (EOS) for dense matter is one of the crucial ingredients in numerical simulations for astrophysical phenomena, such as core-collapse supernovae, cooling of nascent proto-neutron stars, and binary neutron star mergers. While considerable efforts have been devoted to understanding the dense-matter EOS from terrestrial experiments, astrophysical observations, and theoretical calculations, the nuclear EOS still remains rather uncertain. In particular, since the properties of dense nuclear matter appearing in those simulations are governed by the repulsion of nuclear forces, it should be described with a nuclear Hamiltonian composed of realistic nuclear potentials. In the above situation, we have recently constructed a new nuclear EOS based on the variational many-body theory with realistic nuclear forces (AV18 + UIX) [1], and the resultant EOS table is available on the Web [2] for the use in various astrophysical simulations.
In this presentation, we will discuss the properties of our nuclear EOS and its applications to core-collapse simulations starting from several progenitor models to investigate the EOS effects on the mechanism of successful and failed core-collapse supernova explosions. Furthermore, we will report on the newly obtained neutrino-nucleon reaction rates in supernova matter with the consistent variational method, which is an extension of the present EOS.[1] H. Togashi, K. Nakazato, Y. Takehara, S. Yamamuro, H. Suzuki, and M. Takano, Nucl. Phys. A 961 (2017) 78.
[2] http://www.np.phys.waseda.ac.jp/EOS/Speaker: Dr Hajime TOGASHI (Daegu University)
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Lunch break
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Stellar modelling
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The Dawn of 3D Stellar Evolution and Nucleosynthesis
Stars play a key role in the Cosmos through the light they shine, the chemical elements they produce and the kinetic energy they inject into their surroundings via winds and supernova explosions. For many decades, our understanding of the structure, evolution and fate of stars has greatly benefitted from comparing spherically symmetric, one-dimensional (1D) theoretical models to a variety of observations. The large increase in the number and quality of observations combined with the advent of asteroseismology probing the interior of stars, however, has exposed the limitation of 1D models. The increasing computing power available has now reached the point where significant fractions of a star and for an increasing duration can be simulated in 3D using realistic stellar conditions, which represents the dawn of multi-D stellar evolution and nucleosynthesis modelling of stars. In this talk, I will review some of the most critical limitations of 1D models and the latest 3D simulations providing new insight and guidance to improve 1D models and our understanding of stars and their impact.
Speaker: Prof. Raphael HIRSCHI (Keele University) -
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Evolution of accreting white dwarfs in close binary systems including the effects of rotation and magnetic fields and implications for Type Ia supernovae
Accreting white dwarfs in interacting binary systems are closely related to explosive events like novae and Type Ia supernovae, which play an important role in the chemical evolution of the universe. Although numerous studies on the evolution of accreting white dwarfs have been presented in the literature, there has been a relatively limited focus on exploring the impact of rotation and magnetic fields on these systems. Given that the accreted matter is supposed to carry a large amount of angular momentum to spin-up the white dwarf, the resulting rotational and magnetic instabilities would lead to a significant chemical mixing as well as a change of the hydrostatic structure. This can in turn have important consequences in the pre-explosion structure and the nucleosynthesis of novae and supernovae. In this talk, I will present some recent evolutionary models of helium-accreting white dwarfs including these effects and discuss how they can alter our view on the so-called double-detonation scenario for Type Ia supernovae.
Speaker: Sung-Chul YOON (Seoul National University) -
148
On the bridge: Asteroseismology meets nuclear astrophysics in massive stars
Massive stars (10 solar masses and up) play an important role in the synthesis of new elements in the Universe. They enrich the interstellar medium with these newly synthesized isotopes via their stellar winds and via their final supernova explosions. To understand the nuclear yields of these stars, especially before the supernova explosion, there are three key ingredients; the nuclear reaction rates that govern the creation of new isotopes, internal mixing processes that bring the newly synthesized isotopes from the interior of the star to the surface, and the stellar winds that bring these isotopes into the interstellar medium. In our work, we focus on the effects of interior mixing processes on the nucleosynthetic yields. Up to now, the calculations of stellar yields have relied on stellar evolution models that have remained uncalibrated in terms of chemical mixing in the stellar interior. We take the recent observationally driven advances in asteroseismic and binary analysis of the interior structure and evolution of intermediate- to high-mass stars and the proposed mixing profiles based on these observations into account. In this way, our models will bridge the gap between theoretical yield calculations and asteroseismically calibrated mixing profiles. This is a vital step to improve our understanding of the evolution of stars with initial masses of 7-30 solar masses and their role in enriching the galaxy with newly synthesized isotopes. We focus on this mass-range because it includes the most massive asteroseismically constrained stars, and because it covers the stars just below the supernova boundary (8-10 solar masses). Due to the strong dependence between the interior structure of a supernova-progenitor and its final fate, changes in the interior mixing of these stars not only affect the nucleosynthetic yields (both in the stellar winds and from the supernova explosion), but also might affect which stars will end their lives as supernovae and might affect the mass of the supernova remnant. Therefore, a proper understanding of the impact of this calibrated mixing on stellar evolution is especially valuable for the community working on nucleosynthesis and galactic chemical evolution.
Speaker: Hannah BRINKMAN (Institute of Astronomy, KU Leuven) -
149
Nucleosynthesis and stellar evolution in 3D hydrodynamic simulations
Our knowledge of stellar evolution is limited by uncertainties coming from complex multi-dimensional processes in stellar interiors, usually reproduced in 1D stellar models with simplifying prescriptions. 3D hydrodynamic models can improve these prescriptions by studying realistic multi-D processes, usually for a short timerange (minutes or hours). Recent advances in computing resources are starting to enable 3D models to run for longer time and include nuclear reactions, making the simulations more realistic and allowing to study the effects of nuclear reactions on the stellar evolution.
In this talk, I will present results coming from a new set of hydrodynamic simulations of a massive-star burning shell, run continuously from early development to fuel exhaustion, and including different nuclear species. I will discuss the implications for stellar nucleosynthesis, convective boundary mixing, and the possibility of deriving simplifying laws that can be used in 1D stellar models.Speaker: Federico RIZZUTI (Keele University) -
150
The Impact of Binary Evolution on Stellar Nucleosynthesis
Almost all of the nuclei in the cosmos originate from stars. Low-mass (~1-8M⊙) stars are thought to synthesise a large fraction of the universe’s carbon, nitrogen, and fluorine, and about half of all elements heavier than iron making them an important ingredient in galactic chemical evolution (GCE) models. Low mass stars synthesise material through a variety of nuclear processes such as H-burning, He-Burning, and the slow neutron capture process. Most theoretical nucleosynthesis calculations assume that the stars are single, and these calculations are commonly used for GCE models. However, over half of low mass stars are observed to have at least one stellar companion in what is known as a binary system. Binary evolution could lead to mass transfer and stellar mergers which in turn could influence the conditions within the stellar interior. In this talk, we question the use of only single star calculations within GCE models and investigate the influence of binary evolution on the production of carbon-12, nitrogen-14, aluminium-26, and s-process elements (e.g., Pb208) by a low-mass stellar population at solar metallicity. We find that for a stellar population with a binary fraction of 0.7 the overall output of carbon-12 decreases by ~12%, nitrogen-14 decreases by <5%, aluminium-26 increases by ~25%, and lead decreases by <5%. We also find that binary evolution could explain some of the anomalous abundances observed in globular clusters and planetary nebulae.
Speaker: Zara OSBORN (Monash University)
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146
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Coffee break
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Nuclear properties for astrophysics
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151
Experiments related to Neutron-Rich Nuclei in r-Process Nucleosynthesis
Where and how were heavy elements which contain many neutrons relative to proton, synthesized? With regards to the origin of these heavy elements, a reaction in which nuclei capture neutrons in a fast and continuous manner during the explosion of a star was proposed and named the rapid neutron capture process (r process) [1].
In 2017, a binary neutron star merger event was discovered by simultaneous observations of gravitational and electromagnetic waves, and its kilonova was also identified, suggesting the synthesis of heavy elements. Were heavy elements such as gold, platinum, and even uranium synthesized in binary neutron star mergers, supernova explosions, or collapsars [2-4]? Analysis of the unique heavy-element compositions left behind in the solar system, meteorites, and old metal-poor stars has begun. The key to deciphering the traces left behind by isotopic elements lies in the thousands of neutron-rich nuclei that disappeared in an instant.
Here, we introduce the experimental research on the explosive r-process nucleosynthesis and future perspective at RIBF [5,6].[1] E.M. Burbidge, G.R. Burbidge, W.A. Fowler, and F. Hoyle, Rev. Mod. Phys. 29, 547 (1957).
[2] S. Wanajo et al., Astrophys. Jour. Lett. 789: L39 (2014).
[3] C. Kobayashi, A.I. Karakas, and M. Lugaro, Astrophys. Jour. 900, 179 (2020).
[4] J. Barnes and B.D. Metzger, Astrophys. Jour. Lett. 939: L29 (2022).
[5] V.H. Phong et al., Phys. Rev. Lett. 129, 172701 (2022).
[6] S. Nishimura, Prog. Theor. Exp. Phys. 2012, 03C006 (2012).Speaker: Shunji NISHIMURA (RIKEN) -
152
Experimental study on astrophysically important $^{22}$Mg nucleus via resonant scattering of $^{18}$Ne+ $\alpha$
The $^{18}$Ne($\alpha$,$p$)$^{21}$Na reaction is one candidate of the breakout reactions from hot-CNO cycle, and it plays an important role in understanding the X-ray bursts and the nucleosynthesis in the rp-process. We investigated energy levels of the $^{22}$Mg by measuring the $\alpha$ resonant scattering on $^{18}$Ne in inverse kinematics. The $^{18}$Ne rare isotope beam was produced at the CNS Radio-Isotope Beam Separator (CRIB) of Center for Nuclear Study, the University of Tokyo, located at the RIBF of RIKEN Nishina Center. Recoiling $\alpha$ particles were measured by silicon detector telescopes. The excitation function of $^{22}$Mg was obtained for the excitation energies of 10–16 MeV by adopting the thick-target method. To clarify the energy level properties of $^{22}$Mg, the experimental excitation function was compared with theoretical R-matrix analysis using the SAMMY8 code. Since energy levels were not clearly observed at the astrophysically important energy range, upper limits on the $^{18}$Ne ($\alpha$,$\alpha$)$^{18}$Ne cross section were set. The astrophysical impact was also investigated by estimating the $^{18}$Ne($\alpha$,$p$)$^{21}$Na cross section.
Speaker: Soomi CHA (Center for Exotic Nuclear Studies, Institute for Basic Science) -
153
New half-lives and beta-delayed neutron branchings for neutron-rich Ba to Nd nuclei (A~160) relevant for the formation of the r-process rare-earth peak
Rapid neutron capture nucleosynthesis (the r-process) produces nearly half of the nuclei heavier than iron in explosive stellar scenarios.
The solar system r-process residual abundances show two peaks located at $A\sim 130$ and $A\sim 195$. Between these peaks lies the Rare-Earth Peak (REP), a distinct but small peak at mass number $A\sim 160$ that arises from the freeze-out during the final stages of neutron exposure. According to theoretical models and sensitivity studies, half-lives $(T_{1/2})$ and $\beta$-delayed neutron emission probabilities $(P_{xn})$ of neutron-rich nuclei, in the mass region $A\sim 160$ for 55$\le$Z$\le$64 are critical for the formation of the REP [1,2]. The BRIKEN collaboration [3] conducted an extensive measurement program of $\beta$-decay properties of nuclei involved in the r-process at the Radioactive Isotope Beam Factory (RIBF) located in the RIKEN Nishina Center, Japan. The BRIKEN-REP experiment has measured $T_{1/2}$ and $P_{1n}$ of nuclei from Ba to Eu (A $\sim$ 160), belonging to the region that is the most influential to the REP formation [4,5]. In this contribution, we will present the experimental results of new $T_{1/2}$ and $P_{1n}$ branchings within the Ba to Nd region. Furthermore, we will discuss how these new experimental data trends match with the trends from recent nuclear model calculations used for r-process simulations of the REP.[1] M. R. Mumpower et al , Phys. Rev. C 85, 045801 (2012).
[2] A. Arcones and G. Martinez Pinedo , Phys. Rev. C 83, 045809 (2011).
[3] J.L. Tain et. al , Acta physica polonica B 49(03), 417 - 428 (2018).
[4] G. G. Kiss, et al., The Astrophysical Journal 936 2, 107 (2022).
[5] A. Tarifeño-Saldivia et al , RIKEN Accel. Prog. Rep. 54, 27. (2021).Acknowledgements:
This work has been supported by the Spanish Ministerio de Economía y Competitividad under Grants nos. FPA2014-52823-C2-1-P, FPA2014-52823-C2-2-P, FPA2017-83946-C2-1-P, FPA2017-83946-C2-2-P and grants from Ministerio de Ciencia e Innovacion nos PID2019-104714GB-C21 and PID2019-104714GB-C22.Speaker: Max PALLÀS SOLÍS (Universitat Politècnica de Catalunya) -
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Astrophysical Reactions Important in r- and vp- processes Measured Using (d,p) Transfer Reactions at OEDO-SHARAQ
The rapid (r) neutron-capture process produces half of the elements heavier than iron and is located on the neutron-rich side of the nuclear chart. Conversely, light nuclei on the neutron-deficient side may be produced in the neutrino-driven rapid-proton capture (vp) process. Considering the r-process, promising site candidates such as core-collapse supernovae (CCSNe) and neutron star mergers still show large discrepancies between observed and calculated abundances. The calculations rely on neutron-capture cross sections which depend on two reaction processes: direct radiative capture and compound nuclear (CN) mechanism. Neutron capture on $^{130}$Sn strongly influences the final abundances around the second and third r-process peaks, however, the CN mechanism lacks empirical data. Considering the vp-process proposed to occur in the ejecta of CCSNe, this is a promising solution to synthesize isotopes not adequately produced in the rapid-proton (rp) capture process, particularly $^{92,94}$Mo and $^{94,96}$Ru. The $^{56}$Ni(n,p)$^{56}$Co reaction is a crucial branching point between the vp- and rp- processes and thus governs the abundances of heavier elements, however, its cross section lacks measurement. To address these knowledge gaps of the $^{130}$Sn(n,γ) and $^{56}$Ni(n,p) reactions, the surrogate technique was employed using (d,p) transfer reactions on $^{130}$Sn and $^{56}$Ni, respectively, at the BigRIPS-OEDO beamline housed at RIBF in RIKEN, Japan. The radioactive beams were produced and separated by the BigRIPS accelerator. Using OEDO the $^{130}$Sn ($^{56}$Ni) beam was decelerated to ~ 22 (15) MeV/u and focused onto a CD$_{2}$ solid target. Light particles were detected at backward lab angles using the TiNA array. Heavy reaction products were momentum-analyzed by the SHARAQ spectrometer and identified using the B$\rho$-dE-range technique. This approach has a distinct advantage whereby the gamma-emission probabilities of compound nuclear states may be determined with no gamma-ray detection necessary. In this talk, the experimental procedure and preliminary results are presented, with an emphasis on the capabilities of OEDO.
Speaker: Thomas CHILLERY -
155
Bound-state beta-decay of Thallium-205 to constrain s-process predictions for the early Solar System
Bound-state $\beta$-decay ($\beta_b^-$-decay) is a radically transformative decay mode that can change the stability of a nucleus and generate temperature- and density-dependent decay rates. In this decay mode the $\beta$-electron is created directly in a bound atomic orbital of the daughter nucleus instead of being emitted into the continuum, so the decay channel is only significant in almost fully stripped ions during extreme astrophysical conditions. The $\beta_b^-$-decay of $^{205}$Tl$^{81+}$ could influence our understanding of the production of $^{205}$Pb, a short-lived radioactive (SLR, 17.3 Myr) nucleus that is fully produced by the s-process in stars. In the context of the early Solar system, SLRs are defined by half-lives of 0.1-100 My and their abundance in meteorites can be used to constrain the formation of the Solar System [1]. Historically, it has been noted that thermal population of the 2.3 keV state of $^{205}$Pb in stellar conditions could dramatically reduce the abundance of s-process $^{205}$Pb by speeding up the EC-decay to $^{205}$Tl. This destruction of $^{205}$Pb is potentially balanced by the $\beta_b^-$-decay of $^{205}$Tl$^{81+}$ [2]. Currently, a theoretical prediction for the half-life of fully stripped $^{205}$Tl is used in stellar models, but given the importance of the $^{205}$Pb/$^{204}$Pb chronometer, a measurement of the $\beta_b^-$-decay for $^{205}$Tl$^{81+}$ was conducted at the GSI Heavy Ion Facility in March 2020. A $^{205}$Tl$^{81+}$ beam was stored in the Experimental Storage Ring, and the growth of $^{205}$Pb$^{81+}$ daughters with storage time was directly attributable to the $\beta^-_b$-decay channel. We will report the measured half-life and detail how this half-life can be used to more accurately predict the $^{205}$Pb abundance in the early Solar System.
[1] M. Lugaro, et al. Progress in Particle and Nuclear Physics, 102:1–47, 2018.
[2] K. Yokoi, et al. Astronomy and Astrophysics, 145:339–346, 1985.Speaker: Guy LECKENBY (TRIUMF)
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151
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Conference dinner
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Core-collapse supernovae, mergers and the r-process
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156
Probing heavy element nucleosynthesis through electromagnetic observations
Half of the elements heavier than iron are produced by a sequence of neutron captures, beta-decays and fission known as r-process. It requires an astrophysical site that ejects material with extreme neutron rich conditions. Once the r-process ends, the radioactive decay of the freshly synthesized material is able to power an electromagnetic transient with a typical intrinsic luminosity. Such kilonova was observed for the first time following the gravitational signal GW170817 originating from a merger of two neutron stars. This observation answered a long lasting question in nuclear astrophysics related to the astrophysical site of the r process.
In this talk, I will summarize our current understanding of r process nucleosynthesis. I will also illustrate the unique opportunities offered by kilonova observations to learn about the in-situ operation of the r-process and the properties of matter at extreme conditions. Achieving these objectives, requires to address fundamental challenges in astrophysical modeling, the physics of neutron-rich nuclei and high density matter, and the atomic opacities of r-process elements required for kilonova radiative transfer models.
Finally, I will introduce a new nucleosynthesis process, the $\nu r$-process, that operates in ejecta subject to very strong neutrino fluxes producing p-nuclei starting from neutron-rich nuclei. It may solve a long standing problem related to the production of $^{92}$Mo and the presence of long-lived $^{92}$Nb in the early solar system.Speaker: Gabriel MARTÍNEZ-PINEDO (GSI and TU Darmstadt) -
157
Molecule formation in the ejecta of SN 1987A: the impact of effective matter mixing based on 3D hydrodynamical models
More than 30 years after the discovery of SN 1987A, it entered a phase of a young supernova remnant. It is considered that molecules and dust are formed in the ejecta. Actually, recent ALMA observations (Abellán et al. 2017) have revealed that the 3D distribution of carbon monoxide (CO) and silicon monoxide (SiO) is rather non-spherical and lumpy. However, how molecules are formed in core-collapse supernovae has still been unclear. The distribution of seed atoms in the ejecta of SN 1987A, which is affected by matter mixing before the molecule formation, may play a role in the formation of molecules. Therefore, in order to investigate the impact of matter mixing on the formation of molecules in the ejecta of SN 1987A, time-dependent rate equations for chemical reactions are solved (arXiv:2305.02550) for one-zone and one-dimensional ejecta models of SN 1987A based on three-dimensional hydrodynamical models (Ono et al. 2020). It is found that the mixing of $^{56}$Ni could play a non-negligible role in both the formation and destruction of molecules, in particular CO and SiO, through several reaction sequences. Some of the results and how $^{56}$Ni, practically $^{56}$Co, affects the formation and destruction of molecules are presented.
Speaker: Masaomi ONO (Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), Taiwan) -
158
Neutrino-Driven Outflows and the Origin of Light Heavy Elements
The light heavy elements between strontium and silver, can be synthesized in a primary process in either neutron- (weak r-process) or proton-rich (νp-process) neutrino-driven outflows of explosive environments [1]. Constraining the nuclear physics uncertainties, for example the (α,xn) reaction rates in the weak r-process [2,3], allows us to investigate the conditions that create the light heavy elements, by comparing to the abundances of Galactic metal-poor stars. In addition, the study of presolar stardust grains (SiC) can also reveal signatures of neutrino-driven nucleosynthesis in the Galaxy [4]. We have used an extensive library of astrophysical conditions of both neutron- and proton-rich neutrino-driven outflows, as well as combinations of the two to reproduce the abundance patterns observed in metal poor stars with enhanced light neutron-capture element production, such as HD 122563 (Honda star)[5]. Our preliminary results suggest that there are specific combinations of astrophysical conditions that can reproduce the light heavy elemental abundances observed in such stars.
*This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project No. 279384907—SFB 1245, the European Research Council Grant No. 677912 EUROPIUM, and the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006)
References
[1] A. Arcones and F. Montes, Astrophys. J. 731, 5 (2011)
[2] J. Bliss et al., Phys. Rev. C 101, 055807 (2020)
[3] A. Psaltis et al., Astrophys. J. 935, 27 (2022)
[4] A. Psaltis et al. (in preparation).
[5] S. Honda et al., Astrophys. J. 666, 1189 (2007)Speaker: Thanassis PSALTIS (NCSU/TUNL) -
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The p-process nucleosynthesis in core-collapse supernovae
Neutron-capture processes made most of the abundances of heavy elements in the Solar System, however they cannot produce a number of rare proton-rich stable isotopes lying on the left side of the valley of stability. The p-process, or $\gamma$-process, is recognised and generally accepted as a feasible process for the synthesis of proton-rich nuclei in core collapse supernovae. However this scenario still leaves some puzzling discrepancies between theory and observations.
My aim is to explore in more detail the p-process production from massive stars in different sets of models and using the latest nuclear reaction rates. Here I will show some of the result of my analysis, by identifying the p-process sites and focusing on supernova progenitors that experience a C-O shell merger just before the collapse of the Fe core. I will also briefly discuss how the p-process depends on the supernova explosion energy.Speaker: Lorenzo ROBERTI (Konkoly Observatory, CSFK) -
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The neutrino-process in core-collapse supernova with strong magnetic field
A huge number of neutrinos emitted in a supernova explosion interact with a dense plasma. The interaction between neutrinos and electrons remarkably changes the neutrino oscillation probability at the specific electron density, known as the Mikheyev–Smirnov–Wolfenstein (MSW) resonance effect. Previous studies for the neutrino-process in core-collapsing supernova have well-established the effects of neutrino interactions with electrons and neutrino itself on the neutrino process. However, observations on magnetar surfaces imply that a strong magnetic field might exist in supernova environments. It turns out that such a strong or stronger magnetic field can polarize the electrons, whose effective potential, including axial-vector interaction, changes the MSW effect region or the effect of neutrino-neutrino interaction on neutrino oscillation. In this presentation, we show the effects of the strong magnetic field on neutrino oscillation, adopting a power law of electron number density and dipole magnetic field profiles. Also, we discuss those effects through the abundance of $^{92}$Nb, $^{98}$Tc, and $^{138}$La with the SN1987A model.
Speaker: Heamin KO (Soongsil University)
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156
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Coffee break
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The early Universe, galactic evolution
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161
Galactic archaeology with metal-poor stars
TBD
Speaker: Haining LI (National Astronomical Observatories, Chinese Academy of Sciences) -
162
The role of Majorons on big bang nucleosynthesis
The Majoron, the Goldstone boson from the spontaneous lepton number symmetry breaking, is a theoretically and phenomenologically well-motivated hypothetical particle. As it is typically believed to be long-lived, it has the potential power of altering the big bang nucleosynthesis.
We find that non-thermal energetic neutrinos produced by decays of Majoron can cause various neutrino-induced nuclear reactions, providing additional neutrons from the inverse beta decay. It is of great interest to see whether such reactions can boost the reactions such as 7Be(n,p)7Li and 7Li(p,\alpha)4He processes, resolving the long-standing discrepancy between the observed abundance and the theoretical prediction of 7Li. Stating differently, the big bang nucleosynthesis can constrain the values of the parameters of the Majoron. These questions are addressed in our work by studying the effect of the Majoron on the big bang nucleosynthesis.Speaker: Tae-Sun PARK (CENS, IBS) -
163
High-precision nuclear chronometer for the cosmos
Nuclear chronometer provides an independent dating technique for the cosmos by predicting the ages of the oldest stars. Similar to geochronology, the ages are determined by comparing the present and initial abundances of long-lived radioactive nuclides. In nuclear cosmochronology, the present abundances can be obtained from the astrophysical observations whereas the initial abundances have to be determined by simulations of rapid neutron capture (r-process) nucleosynthesis. However, the previous Th/X, U/X, and Th/U chronometers suffer from the uncertainties of the r-process simulations, which leads to a poor identification on the cosmic age. Here we show that the precision of the nuclear chronometer can be significantly improved by synchronizing the three different types of nuclear chronometers, as it imposes stringent constraints on the astrophysical conditions in the r-process simulation. The new chronometer (Th-U-X) reduces the uncertainties of the predicted ages from the astrophysical conditions, more than ±2 billion years for the Th/U chronometer, to within 0.3 billion years. By the Th-U-X chronometer, ages of the six metal-poor stars with observed uranium abundances are estimated to be varying from 11 to 17 billion years, two of which disfavor the young cosmic age of 11.4 billion years by a recent measurement of Hubble constant from angular diameter distances to two gravitational lenses. Our results demonstrate that the Th-U-X chronometer provides a high-precision dating technique for the cosmic age. For perspective, the Th-U-X chronometer can serve as a standard technique in nuclear cosmochronology. It will be even more appealing in case that the r-process site is identified whereas the corresponding detailed conditions remain unknown, as it can filter out unreasonable conditions by synchronizing nuclear chronometers.
Speaker: Xinhui WU (Peking University)
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161
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Lunch break
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Nuclear properties for astrophysics
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Constraining the key reaction rates using indirect methods
Indirect methods play an important role in constraining the astrophysical rates of nuclear reactions. This talk will review several recent indirect studies that provided almost model-independent constraints for the key rates.
Neutron-upscattering enhancement of the triple-alpha reaction responsible for the production of carbon, suggested in [1], was investigated by measuring a time-inverse process, 12C(n,n’)12C(Hoyle), using the Texas Active Target Time Projection Chamber [2]. The total cross section for inelastic neutron scattering in carbon was measured in a wide range of energies, and the detailed balance and R-matrix analysis was used to establish the 12C(Hoyle)(n,n’)12C reactions cross section at astrophysically relevant energies [3].
The radiative width of the Hoyle state has a direct impact on the triple-alpha reaction rate. Recent measurements by Kibedi [4] reported a radiative width significantly above the previously recommended value [5]. I will report the results of the new study performed at the Cyclotron Institute, Texas A&M University, which provides a definitive resolution to the controversy.
The α-cluster properties of the ground state of 16O (the alpha asymptotic normalization coefficient, ANC) influence the low energy extrapolation for the key 12C(α,γ)16O reaction rate [6]. The new measurements at Texas A&M University used 12C(20Ne,16O)16O alpha-transfer reaction at sub-Coulomb energy to provide nearly model-independent constraints to the respective ANC values.[1] M. Beard, S.M. Austin, R. Cyburt, Phys. Rev. Lett., 119, 112701 (2017).
[2] E. Koshchiy, et al., Nucl. Inst. Meth. Phys. Res. A, 957, 163398 (2020).
[3] J. Bishop, et al., Nature Communications, 13, 2151 (2022).
[4] T. Kibedi, et al., Phys. Rev. Lett., 125, 182701 (2020).
[5] M. Freer and H. Fynbo, Prog. Part. Nucl. Phys., 78, 1 (2014).
[6] R.J. deBoer, et al., Rev. Mod. Phys., 89, 035007 (2017).Speaker: Prof. G.V. ROGACHEV (Department of Physics and Astronomy, Texas A&M University) -
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Novel Studies of Nucleosynthesis in the Lab
A variety of nucleosynthesis processes operate in our universe, producing elements across the nuclear chart. Using a range of tools and techniques, we can probe the nuclear reactions that comprise these processes. In explosive rp-process environments, direct reactions are possible using gaseous targets such as JENSA, with input from indirect techniques such as transfer reactions on both stable and radioactive isotopes. The role of long-lived isomeric states in rp-process nuclei, just as in 26Al, is beginning to be studied experimentally using beams of mixed ground state and isomer content, with indirect studies underway to populate the nuclear levels of interest, and direct measurements with SECAR planned. In supernovae, the mechanisms producing the rare p-process nuclei are being studied using monoenergetic gamma beams at the HIgS facility at TUNL. In this talk, I will provide a brief survey of these different experimental campaigns, and discuss the preliminary results and future directions.
Speaker: Kelly CHIPPS (Oak Ridge National Laboratory) -
166
Impact of the Hoyle state in 12C on hypernova neutrino-p process and Galactic chemical evolution
The hadronic deexcitation of the Hoyle state in 12C induced by inelastic scatterings of particles can enhance the triple-alpha reaction and the resultant accumulated seed nuclei prevent the synthesis of the heavier elements [1]. Quite recently, neutron-induced deexcitation cross sections were measured experimentally and this effect turns out to be less significant [2]. It therefore is even more interest to explore if the protons or alpha-particles could make a significant effect on the explosive nucleosynthesis in proton-rich environment. We study the impact of such particle-induced Hoyle state deexcitation on the νp-process nucleosynthesis in proton-rich ν-driven winds of core-collapse supernovae (CCSNe). We find that the productions of p-nuclei such as 92,94Mo and 96,98Ru are suppressed due to the effect of Hoyle state deexcitation in the wind models of ordinary CCSNe. On the other hand, we find also that these isotopic abundances are enhanced in explosive nucleosynthesis in an energetic hypernova (HN) wind models [3]. We then apply our new HN nucleosynthesis results to the Galactic chemical evolution of 92,94Mo and 96,98Ru, resulting in an interesting fact that the HN νp-process can enhance the calculated solar isotopic fractions of these p-nuclei, whose isotopic fractions are 1-2 orders of magnitude larger than the ordinary p-nuclei, regardless of the particle-induced Hoyle state deexcitation [3].
[1] S. Jin, L. F. Roberts, S. M. Austin & H. Schatz, Nature 588 (2020), 57.
[2] J. Bishop, C. E. Parker, G. V. Rogachev, et al., Nature Comm. 13 (2022), 2151.
[3] H. Sasaki, Y. Yamazaki, T. Kajino & G. J. Mathews, (2023) submitted.Speaker: Taka KAJINO (Beihang University/NAOJ/University of Tokyo) -
167
Study of two missing states of $^{19}$Ne affecting the $^{18}$F($p, \alpha$)$^{15}$O reaction rate in classical novae
Knowledge of the $^{19}$Ne resonance information near the proton threshold (E$_{x}$=6.410 MeV) is important for studying the $^{18}$F($p$,$\alpha$)$^{15}$O nuclear reaction rate in a classical nova [1-4]. Several states in the vicinity of the proton threshold still have not been observed in $^{19}$Ne but were predicted by assuming isospin symmetry from its mirror state in $^{19}$F [5,6]. The $\alpha$-elastic scattering experiment in a Thick Target Inverse Kinematics method (TTIK) was performed at RIKEN using the CNS RI Beam separator (CRIB) with a $^{15}$O radioactive beam for investigating the $^{19}$Ne level structure [7,8]. Two missing states were identified near the proton threshold, and one of the missing states affects the $^{18}$F($p$,$\alpha$)$^{15}$O reaction rate. Additionally, the candidates of rotational bands for the alpha cluster structure were measured. Experimental details and results will be discussed in the presentation.
[1] J. Jose et al., Eur. Phys. J. A 27, 107 (2006).
[2] A. Coc et al., Astron. and Astrophys. 357, 561 (2000).
[3] K. Chae et al., Phys. Rev. C 74, 012801 (2006).
[4] D. Kahl et al., Astron. and Astrophys. 653. A64 (2021).
[5] N. C. Shu et al., Phys. Rev. C 58, 1354 (1998).
[6] C. D. Nesaraja et al., Phys. Rev. C 75, 055809 (2007).
[7] Y. Yanagisawa et al., Nucl. Instrum. Methods Phys. Res. A 539, 74 (2005).
[8] H. Yamaguchi et al., Nucl. Instrum. Methods Phys. Res. A. 589, 150 (2008).Speaker: D. KIM (Center for exotic nuclear studies, Institute Basic Science) -
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Nuclear Physics of Accreting Neutron Stars
I will review the current understanding of the nuclear physics of accreting neutron stars, including the rp-process and processes involving neutron rich nuclei, and their relation to observables such as X-ray bursts and the cooling of transiently accreting neutron stars. This will include new results from experiments on rp-process reactions and measurements related to crust Urca processes, modeling results using updated reaction libraries, nuclear physics sensitivity studies, and an overview of the new opportunities opened up by new radioactive beam facilities such as FRIB.
Speaker: Hendrik Schatz (RAHUL JAIN)
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164
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Closing
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