OMEG 2017, International Symposium on Origin of Matter and Evolution of Galaxies, Daejeon, Korea, JUNE 27-30, 2017

27 Jun 2017, 08:00 → 30 Jun 2017, 18:10 Asia/Seoul

Hotel ICC, Daejeon, Korea

We are pleased to announce that the International Symposium on Origin of Matter and Evolution of Galaxies (OMEG 2017) will take place at Hotel ICC in Daejeon, Korea, June 27-30, 2017. This symposium is the 14th symposium of the series, started in 1988, on nuclear astrophysics and related fields. OMEG 2017 will provide a melting furnace of physics, astrophysics, astronomy, cosmology, and related fields to enhance our understanding of origin of matter and evolution of universe.

Topics to be covered include

• Big Bang Cosmology and Primordial Nucleosynthesis
• First Generation Stars and Galactic Chemical Evolution
• Astronomical Observations with Light, X-Ray, Gamma-Ray, and Cosmic-Ray
• Stellar Evolutions and Hydrostatic Burning Processes
• Experimental Nuclear Physics for Astrophysics
• Theoretical Nuclear Physics for Astrophysics
• Explosive Stellar Objects and Nuclear Physics
• Meteorite Analysis and Isotopic Abundance
• Nuclear Matter and Neutron Stars
• Nuclear Data for Astrophysics and Related Topics
• Underground Nuclear Astrophysics
• Next generation RI Beam Facilities for Nuclear Astrophysics

Important Dates

• February 10, 2017: Second circular 
• March 20, 2017: Last day of early registration 
• March 25, 2017: Last day for Hotel ICC reservation 
• April 11, 2017: Registration closed
• April 17, 2017: Abstract submission closed
• May 18, 2017: Final circular
 

Contacts

omeg2017@ibs.re.kr

 

For VISA application

Ms. Jeehyun Cho

e-Mail : jeanne@ibs.re.kr

Phone : +82-42-878-8857

 

Sponsors

         

  

Circular

• Final circular
• First circular
• Second circular

Tuesday, 27 June

Registration

Openning Session (Chair: K. I. Hahn)

1 Openning Session

Speaker: Sunchan Jeong

Session 1 (Chair: Y. S. Lee)

2 Observational constraints on first-star nucleosynthesis

Over the past 25 years, it has been recognized that the light element carbon plays a crucial role in the early chemical enrichment of the Universe. One fundamental observation is that the frequency of the so-called carbon-enhanced metal-poor (CEMP) stars in the Milky Way increases dramatically with decreasing iron abundance – from 20% of all stars with [Fe/H] < -2.0 to > 80% of stars with [Fe/H] < -4.0. Recent discoveries of enhanced carbon in damped Lyman alpha systems at high redshift reveal that the abundance patterns observed in this gas are commensurate with a sub-class of the CEMP stars, the so-called CEMP-no stars, which exhibit little or no enhancement of their neutron-capture elements – providing one of the first direct observational linkages between the high-z Universe and presently observed stars in the Galaxy. I summarize recent progress on our understanding of the production of carbon by first-generation stars, and the powerful constraints that this information provides on Galactic chemical evolution models, the initial mass function in the early Universe, and the nature of first-star nucleosynthesis.

Speaker: Timothy Beers

Slides T.Beers-OMEG2017.pdf

3 New site for neutron-capture in population III and population II stars

We propose a new site for neutron-capture process in massive metal-free and metal-poor stars during the late stages of their evolution. We find that a wide range of neutron-capture abundance patterns can be produced which can explain origin of neutron capture elements observed in many metal-poor stars including CEMP-s, CEMP-rs, and CEMP-no stars. This can fundamentally change our understanding of the origin of heavy elements as well as the evolution of the early Galaxy and the nature of first stars.

Speaker: Projjwal Banerjee

4 Blocking metal accretion onto population III stars by stellar wind

Low-mass population III (PopIII) stars of $< 0.8 M_{\odot}$ could survive up until the present, if they were formed. Non-detection of low-mass PopIII stars in our Galaxy has already put a stringent constraint on the initial mass function (IMF) of PopIII stars, suggesting that PopIII stars have a top-heavy IMF. On the other hand, some claims that the lack of such stars stems from metal enrichment of their surface by the accretion of heavy elements from interstellar media (ISM). We investigate effect of the stellar wind on the metal accretion onto low-mass PopIII stars because, in the heliosphere, it is known that the accretion of the local ISM is prevented by the solar wind even for neutrals. The stellar wind and radiation of low-mass PopIII stars are modeled based on studies of nearby low-mass stellar systems including our Sun. We find that low-mass PopIII stars traveling across the Galaxy forms the stellar magnetosphere during most of their life. Once the magnetosphere is formed, most of neutral interstellar particles are photoionized before reaching to the stellar surface and are blown away by the wind. Especially, the accretion abundance of iron will be reduced by a factor of $< 10^{-12}$ compared with Bondi-Hoyle-Lyttleton accretion and the observed metallicities down to ${\rm [Fe/H]} \sim -5$ are not realized. This demonstrates that low-mass PopIII stars remain pristine and will be found as metal free stars and that further searches for them are important to constrain the IMF of PopIII stars.

Speaker: Shuta Tanaka

Slides T.Shuta-OMEG2017.pdf

5 Lithium-rich very metal-poor stars discovered with LAMOST and Subaru

Lithium is a unique element that is produced in the Big Bang nucleosynthesis but is destroyed by nuclear reactions inside stars. As a result, almost constant lithium abundance is found in unevolved main-sequence metal-poor stars, although the value is systematically lower than that expected from standard Big Bang nucleosynthesis models, whereas lithium abundances of red giants are more than one order of magnitudes lower than those of unevolved stars. There are, however, a small fraction of metal-poor stars that show extremely high lithium abundances, which is not explained by standard stellar evolution models. We have discovered 12 new very metal-poor stars that have enhancement of lithium by more than 10 times compared with typical metal-poor stars at similar evolutionary stages by the large-scale spectroscopic survey with LAMOST and the follow-up high-resolution spectroscopy with the Subaru Telescope. The sample shows a wide distribution of evolutionary stages from subgiants to red giants with the metallicity of -3.3<[Fe/H]<-1.6. The chemical abundance ratios of other elements have been obtained by our spectroscopic study, and estimates of the binary frequency by radial velocity monitoring is ongoing. The observational results provide very new constraints on the scenarios to explain lithium-rich metal-poor stars, such as extra mixing during the evolution along the red giant branch, mass-transfer from a companion AGB star, and engulfment of planet-like objects. These explanations are very unlikely for at least some of lithium-rich objects in our sample, suggesting a new mechanism that enhances lithium during the low-mass star evolution.

Speaker: Wako Aoki

Coffee break

Session 2 (Chair: K. I. Hahn)

6 Impact of the $^{26m}$Al (p,$\gamma$) reaction to galactic $^{26}$Al yield

Astrophysical observables that are directly linked to nuclear physics inputs provide critical and stringent constraints on nucleosynthetic models. As $^{26}$Al was the first specific radioactivity observed in the Galaxy, its origin has fascinated the nuclear astrophysics community for nearly forty years. Despite extensive research, the precise origins of $^{26}$Al remain elusive. At present, the sum of all putative stellar contributions generally overestimates the $^{26}$Al mass in the interstellar medium. Among the many reactions that influence the yield of $^{26}$Al, radiative proton capture on its isomer $^{26m}$Al is one of the least constrained by experimental data. To this end, we developed a $^{26}$Al isomeric beam and performed proton elastic scattering to search for low-spin states in $^{27}$Si. The experimental method and the preliminary results of this on-going study will be presented.

Speaker: Daid Kahl

Slides D.Kahl-OMEG2017.pdf

7 Non-extensive statistics solution to the cosmological lithium problem

Big Bang nucleosynthesis (BBN) theory predicts the abundances of the light elements D, $^3$He, $^4$He and $^7$Li produced in the early universe. The primordial abundances of D and $^4$He inferred from observational data are in good agreement with predictions, however, the BBN theory overestimates the primordial $^7$Li abundance by about a factor of three. This is the so-called ‘cosmological lithium problem‘. Solutions to this problem using conventional astrophysics and nuclear physics have not been successful over the past few decades, probably indicating the presence of new physics during the era of BBN. We have investigated the impact on BBN predictions of adopting a generalized distribution to describe the velocities of nucleons in the framework of Tsallis non-extensive statistics. This generalized velocity distribution is characterized by a parameter $q$, and reduces to the usually assumed Maxwell-Boltzmann distribution for $q$ = 1. We find excellent agreement between predicted and observed primordial abundances of D, $^4$He and $^7$Li for $1.069\leq q \leq 1.082$, suggesting a new solution to the cosmological lithium problem. We encourage studies to examine sources for departures from classical thermodynamics during the BBN era so as to assess the viability of this mechanism. Furthermore, the implications of non-extensive statistics in other astrophysical environments should be explored as this may offer new insight into stellar nucleosynthesis.

Speaker: Jianjun He

8 Measurement of beam characteristics of Low-Energy Accelerators

China JinPing underground Laboratory (CJPL) was established inside the tunnels piercing Jinping Mountain in Sichuan Province, China, which can provide an ideal environment for low background experiment. A new 400 kV accelerator, with high current based on an ECR source, will be placed at this underground laboratory for nuclear astrophysics experiment (JUNA). Due to the new accelerator still being under construction, the resonance reactions, like $^{27}$Al(p, $\gamma$)$^{28}$Si and $^{24}$Mg(p, $\gamma$)$^{25}$Al, and non-resonance $^{12}$C(p, $\gamma$)$^{13}$N was studied at 320 kV high-voltage platform at IMP to estimate the proton beam characteristics, like absolute energy, energy spread, and long-term energy stability. The results of experiment and current state of new 400 kV accelerator will be given.

Speaker: Shuo Wang

Slides S.Wang-OMEG2017.pdf

Symposium Lunch

Session 3 (Chair: Y. K. Kwon)

9 Rare Isotope Science Project in Korea

The use of rare isotopes existing in the world only at a very short moment (radioactivity with short lifetime) is increasing nowadays in various research fields, not only for basic researches in nuclear physics investigating origin of matter, synthesis of new atomic elements, and exotic nuclear structure of rare isotopes but also for applied researches in medical-bio-life science, materials and nuclear sciences. In Korea, a new heavy-ion (HI) accelerator complex, RAON (Rare isotope Accelerator complex for ON-line experiments), is under construction at Daejeon. Fully utilizing the conventional diversity of HI beams, in addition to the new availability of rare isotope (RI) beams, RAON is intended to become one of the world-leading HI beam facilities. RAON could provide new research opportunities in rare isotope science, which is recently attracting many interdisciplinary scientists, manifesting itself in the form of a second renaissance in heavy ion science. Powered by a 400-kW superconducting heavy ion linear accelerator, RAON is intended to establish the In-flight Fragment (IF) and Isotope Separation On-Line (ISOL) facilities. The ISOL facility derived by a 70-MeV cyclotron could induce U-fission with a rate of 1014 fissions/s in maximum. The fission-product (FP) beam isolated by the ISOL will be post-accelerated by a superconducting linear accelerator SCL3 for low energy experiments (up to 18.5MeV/u for the beam of A/q~7). The IF facility will be derived by a 400kW superconducting linear accelerator system, SCL1 and SCL2, where U beam could be accelerated up to 200MeV/u. The post-accelerated FP beams can be injected to the SCL2 for further acceleration, e.g. up to about 250MeV/u for 132Sn, and then can derive the IF facility for producing more exotic rare isotope beams. The combined operation of the ISOL and IF facilities is unique feature of RAON, allowing to reach more than 80% of the unexplored region in the chart of nuclide. Prototyping major accelerator components is almost complete, and the fabrication of major components will start soon. Especially putting the highest priority for early completion of the low-energy facility by the end of 2019, the process for the procurements of major components of the SCL3 is underway. The low-energy facility consisting of the cyclotron, ISOL and SCL3 will deliver various stable and RI beams with variable energy from around 500keV/u (RFQ linac energy) to the energies in maximum around between 18.5 MeV/u (U) and 90 MeV (p) according to their A/q values, to the very low- and low-energy experimental halls. This facility, though part of the full facility, is supposed to be unique and hence highly competitive machine in terms of available beam energy and variety of beam. Following a brief overview of the project and facility RAON, the progress on the development of some components, especially important for an accelerator system to be integrated at an off-site test facility for demonstrating the successful operation of the front-end of the RAON, is presented.

Speaker: Sunchan Jeong

10 Astrophysics related programs at Center for Underground Physics (CUP)

The main theme of the Center for Underground Physics (CUP) at Institute for Basic Science (IBS) is to search the dark matter and neutrino-less double beta decays. I will describe the astrophysical aspects of these two programs. In addition to these programs, I will discuss about the recent short baseline reactor neutrino experiment (NEOS) for sterile neutrino searches and the astrophysical consequences of the result. CUP also has facilities for ultra-low background measurements, and conduct a few search experiments for rare nuclear decays and will describe the relevance to the astrophysics.

Speaker: Yeongduk Kim

11 Using the recoil mass seperator DRAGON to constrain astrophysical reaction rates

The detector of recoils and $\gamma$-rays of nuclear reactions (DRAGON) is used to directly observe radiative capture reactions of astrophysical interest and is located at TRIUMF, Canada. Such measurements are crucial for constraining the uncertainty of nuclear reaction rates, leading to a better understanding of various stellar scenarios. In this talk, DRAGON's measurements of the $^{18}$F($p$,$\gamma$)$^{19}$Ne and $^{76}$Se($\alpha$,$\gamma$)$^{80}$Kr reactions, relevant to satellite observation of novae and the production of heavy proton rich nuclei respectively, are highlighted.

Speaker: Charles Akers

12 New candidates for relic anti-neutrino capture experiments

The low energy nuclear beta or electron capture (EC) decays are excellent tools for testing non-zero neutrino masses. Among all beta unstable nuclides, $^{3}$H, $^{187}$Re, and $^{163}$Ho are attractive for non-zero neutrino mass experiment due to their low Q-values. The EC decay of the isotope $^{163}$Ho has been proposed since a long time as a candidate for measuring the electron neutrino mass and the interest in $^{163}$Ho has been renewed because of a possible relic antineutrino capture experiment. But if there is no overdensity in the $\nu$ distribution, the detection using $^{163}$Ho is not possible. In this talk, we will present new possible candidates for relic anti-neutrino capture experiments using EC decaying nuclei.

Speaker: Jeong-Yeon Lee

13 Unbound states in 17C probed via single-neutron removal from 18C at 245 MeV/u

A study of unbound states in 17C by means of one-neutron knockout from first moving 18C beam at an energy of 245 MeV/u on a carbon target was performed at RIKEN-RIBF laboratory utilizing SAMURAI [1]. The energy spectrum of unbound 17C constructed from momentum vectors of the forward going beam velocity 16C fragment and neutron covered an energy range of the decay neutron below about 6 MeV in the center of mass of 17C*. The adopted experimental scheme was featured by (1) high detection efficiencies for decay neutrons which inherently acquire high velocity in the laboratory, (2) large coverage of phase space of the final decaying system due to kinematical focusing of decay products toward forward angles, (3) large geometrical acceptance down to a vanishing relative energy Erel ensured by magnetic separation of charge fragments and neutrons, (4) maintained good Erel resolution well suited for spectroscopy. The Erel spectrum was characterized by two resonances at Erel=1.92 and 3.24 MeV and a bump at Erel~0.7 MeV. With Sn=0.735(18) MeV, the former two states turned out to correspond to the Ex=2.71(2) and 3.93(2) MeV states reported in a β-delayed neutron spectroscopy study of 17B [2], where respective Jπ assignments of 1/2- and 3/2- have been suggested with the assumption that these were populated through the Gamow-Teller transition. Momentum distributions of the knockout residue for the corresponding states, well matched to those of p-wave neutron removal, provided a model independent confirmation of negative parity assignments for these states. The proposed level scheme of 17C was compared with a range of different shell-model predictions; it turned out that the YSOX shell-model interaction [3], developed from the monopole-based universal interaction and incorporating a larger model space in terms of $\hbar\omega$, gave a consistent account of it, including the locations of the 1/2- and 3/2- cross-shell states. [1] T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res., Sect. B 317, 294 (2013). [2] H. Ueno et al., Phys. Rev. C 87, 034316 (2013). [3] C. Yuan et al., Phys. Rev. C 85, 064324 (2012).

Speaker: Yoshiteru Satou

Slides Y.Satou-OMEG2017.pdf

Coffee break

Session 4 (Chair: P. Papakonstantinou)

14 Eos for neutron stars and core-collapse supernovae

Modelling compact stars is a complex task which depends on many ingredients, among others the properties of dense matter. In this talk I will discuss models for the equation of state (EoS) of dense matter, relevant for the description of core-collapse supernovae, compact stars and compact star mergers. Such EoS models have to cover large ranges in baryon number density, temperature and isospin asymmetry. The characteristics of matter change dramatically within these ranges, from a mixture of nucleons, nuclei, and electrons to uniform, strongly interacting matter containing nucleons, and possibly other particles such as hyperons or quarks. The Eos models will be confronted with relevant experimental and observational constraints. I will highlight some implications for compact star astrophysics.

Speaker: Micaela Oertel

Slides M.Oertel-OMEG2017.pdf

15 Constraining the mass and radius of neutron star by future observations

The mass and radius of neutron star (NS) in the low mass X-ray binary (LMXB) can be measured simultaneously when the observed lightcurve and spectrum show the photospheric radial expansion (PRE). Precise measurements require the distance to the target, information on the radiating surface, and the composition of accreted material. Future observations with large ground-based telescopes such as Giant Magellan Telescope (GMT) and Thirty Meter Telescope (TMT) may reduce the uncertainties in the mass and radius of NS because they could provide information on the composition of accreted material by identifying the companion stars in LMXB. We investigate these possibilities and present our results for selected targets.

Speaker: Kyujin Kwak

Slides K.Kwak-OMEG2017.pdf

16 Relativistic electron-positron plasma screening in astrophysical environments

If an astrophysical environment is hot enough (greater than approximately 0.5 MeV or so), screening in the associated nuclear reactions can be modifed by the presence of a relativistic electron-positron plasma. For non-zero electron chemical potentials, the effect is compounded as the relativistic Debye length in a plasma can be much lower than the classical Debye length. The screening is then enhanced beyond the commonly used classical approximation. This can result in a further enhancement of nuclear reaction rates, and the reaction rate enhancement factor is studied in several relevant scenarios. For sub- or near-threshold resonances, this could potentially change the reaction rates by a significant amount as the reaction energy effectively shifts the resonance above or below threshold. Possible sites where relativistic plasma screening could have a significant effect on results include Big Bang Nucleosynthesis, alpha-rich freezout in the r-process, x-ray bursts, type Ia supernovae, and late-stage burning in massive stellar cores. Current results will be presented in which relativistic plasma effects in high-temperature and high-density environments have been studied. In addition, plasma screening is extended into the intermediate screening regime by exploring higher-order terms in the Poisson-Boltzmann equation.

Speaker: Michael Famiano

17 Nuclear matter and nuclei in parity doublet model

Dense nuclear matter is closely related to heavy ion collisions, nuclear structure, compact stars, etc. We discuss the properties of isospin asymmetric dense matter in an extended parity doublet model [1]. We are especially interested in the role of the delta baryon in dense matter to investigate a transition to delta matter [2]. In addition, we are also interested in the origin of the nucleon mass in dense matter. In the parity doublet model the nucleon mass gets, in addition to the mass from spontaneous chiral symmetry breaking, an additional contribution from the chiral invariant mass. Therefore, it is important to estimate the chiral invariant mass portion of the nucleon mass compared to that from chiral symmetry breaking in dense matter. We also study nuclear structure in the parity doublet model to see if there is any physical observable sensitive to the chiral invariant mass [3]. References: 1) Y. Motohiro, Y. Kim, M. Harada, Phys. Rev. C92 (2015) 025201 2) Y. Takeda, Y. Kim and M. Harada, arXiv:1704.04357 [nucl-th]. 3) W. -G. Paeng, et al, in preparation

Speaker: Youngman Kim

Slides Y.Kim-OMEG2017.pptx

Wednesday, 28 June

Registration

Session 5 (Chair: N. Tominaga)

18 Massive stars evolution and nucleosynthesis

Speaker: Raphael Hirschi (Keele U.)

Slides R.Hirschi-OMEG2017.pdf

19 Evolution of massive binary stars and its implications for the chemical evolution

A large fraction of massive stars are found to be in close binary systems. Binary interactions including exchanges of mass and angular momentum via mass transfer and tidal synchronization can greatly affect the evolution of massive stars. This has many important implications for hydrogen-deficient supernovae, hypernovae, formation of compact binaries (neutron stars and black holes), and nucleosynthesis. In this talk, I will review recent progresses in the theoretical studies of massive binary stars and discuss how binary star evolution is related to some aspects of chemical evolution of galaxies. In particular, I will emphasize the role of rotationally induced chemical mixing resulting from binary interactions, non-conservative mass transfer, and prolonged delay times of core-collapse supernova progenitors.

Speaker: Sung-Chul Yoon (Seoul national university)

Coffee break

Session 6 (Chair: M.-K. Cheoun)

20 Solving the mystery of r-process and $\nu$p-process

The origin of both neutron-rich and proton-rich heavy elements has not yet been clearly understood although sixty years have already passed since B2FH (1957). Core-collapse supernova (SN) or binary neutron-star merger (NSM) is undoubtedly a viable candidate site for these heavy elements. We will first discuss the effects of neutrino interactions and oscillations on the r-process and νp-process nucleosyntheses which depend strongly on n/p ratio in the outflows from CCSN and NSM. We also discuss the critical roles of (n,p) and (n,γ) reactions on the proton-rich nuclei in the νp-process nucleosynthesis, and those of (n,γ) reactions, beta decays, and fission recycling on the neutron-rich nuclei in the r-process nucleosynthesis, respectively. As for the origin of r-process (in neutron-rich outflows), magneto-rotationally driven jet (MHD-Jet) CCSN naturally explains the ”universality” in the observed abundance pattern between the solar-system and extremely metal-poor halo stars in the Milky Way and Ultra-Faint Dwarf Galaxies. NSM has a serious difficulty that their arrival delays due to very slow GW radiation by at least 100 My, which therefore could not contribute to the early galaxies. We propose a model such that the MHD-Jet CCSN contributed first to enrich heavy elements in the early galaxies, then the NSM follows gradually towards the solar system [1-3]. In the proton-rich sides of heavy elements, the origin of $^{92,94}$Mo, %^{96,98}$Ru and several others is a long standing mystery. Although X-ray bursts are the potential candidates for these p-elements, their frequency and ejection mechanism into space are unknown. We will propose an alternative site of the outflow from CCSN that could turn into proton-rich condition due to the quantum effects of neutrino collective oscillations and serve as vital astrophysical site for the production of these p-elements [4]. As such, both neutron-rich and proton-rich outflows from CCSN could be extremely significant source of heavy elements, where the neutrino effects and the (n,γ), (n,p), beta decay and fission reactions control the nucleosynthetic conditions. References: [1] Y. Hirai, Y. Ishimaru, T.R. Saitoh, M.S. Fujii, J. Hidaka & T. Kajino, ApJ 814 (2015), 4; Y. Hirai, Y. Ishimaru, T.R. Saitoh, M.S. Fujii, J. Hidaka & T. Kajino, MNRAS 466 (2017) 2472. [2] S. Shibagaki, T. Kajino, G.J. Mathews, S. Chiba, S. Nishimura & G. Lorusso, ApJ 816 (2016) 79; S. Shibagaki, T. Takiwaki & T. Kajino (2017), in preparation. [3] T. Kajino & G. J. Mathews, ROPP. (2017), in press. [4] H. Sasaki, T. Kajino, T. Takiwaki, T. Hayakawa, A.B. Balantekin & Y. Pehlivan, PRD (2017), submitted.

Speaker: Toshitaka Kajino (NAOJ, U. of Tokyo)

Slides T.Kajino-OMEG2017.pdf

21 r-process nucleosynthesis in several astrophysical scenarios

The r-process nucleosynthesis has been considered to occur in explosive astronomical phenomena relevant to neutron stars, e.g. core-collapse supernovae and mergers of compact-object (neutron stars/black holes) binaries. However, The detailed quantitative properties in astrophysical models for the r-process are not completely understood yet. In this talk, I will show recent results of r-process nucleosynthesis in neutron star mergers, based on our collaboration. As mass ejection through neutron star mergers has several phases with different nucleosynthesis composition, I will discuss nucleosynthesis yields on the dynamical ejecta and neutrino-driven ejecta separately. I also discuss the possibility of r-process in magneto-rotational driven supernovae, as an alternative r-process scenario in the early galaxies.

Speaker: Nobuya Nishimura (Keele U.)

22 Enrichment of neutron-rich elements by massive stars and neutron-star mergers in galatic history

The data on abundances of neutron-rich elements in metal-poor stars of the Galactic halo and dwarf galaxies are diverse and difficult to interpret. I argue that this is mostly due to the multiple mechanisms producing such elements in the early universe. An additional complication is caused by the mixing of nucleosynthetic products from various sources in the framework of hierarchical structure formation at early times and then in a prototypical galactic disk.

Speaker: Yong-Zhong Qian

Lunch & Excursion

Banquet

Thursday, 29 June

Session 7 (Chair: K. Chae)

23 Experimental challenge to the big-bang nucleosynthesis

The primordial nucleosynthesis(BBN) right after the big bang (BB) is one of the key elements that support the BB model. The BBN is well known that it produced primarily light elements, and explains reasonably most of the element abundances. However, there remains some interesting and serious questions. One is an abundance problem, called the Li problem. The BBN simulations using recent detailed micro-wave background measurements explain most light elements including D, 4He, etc, but the 7Li abundance is over predicted roughly by a factor of three, which is called the Li problem in BBN. The primordial 7Li was considered to be produced mostly by the electron capture of 7Be in the late stage of BBN. Thus, the question for nuclear physics side is whether 7Be is overproduced or less destructed during the BBN stage. Since the production of 7Be is by the 3He(α,γ) reaction which is quite well known, the problem may be the destruction rate of 7Be. The 7Be(n,p) reaction is considered to be the main destruction reaction, but it is well investigated. Thus, it seems hard to change the rate by a factor of three. The next possible channel was the 7Be(n,α) reaction, and almost no experimental works reported before [1]. Recently, several experiments [2,3] were performed or being performed by the direct and indirect methods. I will discuss the reaction studies of 7Be(n,α) including our result[3]. The conclusion is that the reaction rate proposed by Wagoner et al., which is currently being adopted, is roughly one order of magnitude too large. Thus, the Li problem was not solved, giving a more difficulty. Another interesting question for the BBN is the production of heavier elements like B, C, and O in the primordial nucleosynthesis. This production would have influenced the evolution of the first generation stars. But, it is not known well because lack of experimental data and astronomical observations. This problem is also a common question of breakout from the pp-chain region to the CNO region at high temperatures like in the νp-process in type II super novae. For this problem, alpha induced reactions are expected to play a crucial role. I will touch also on this subject. References: [1] S.Q. Hou, J.J. He, S. Kubono, and Y.S. Chen, Phys. Rev. C 91 (2015) 055802 [2] M. Barbagallo, et al., Phys. Rev. Lett. 117 (2016) 152701 [3] T. Kawabata, et al., Phys. Rev. Lett. 118 (2017) 052701

Speaker: Shigeru Kubono

24 Nuclear astrophysics experiments with reaccelerated beams at NSCL

Speaker: Tony Ahn

25 Measurements of the neutron-induced reactions on 7Be with CRIB by the Trojan Horse method

It has been known that the prediction of the primordial $^7$Li abundance by the standard Big-Bang Nucleosynthesis (BBN) model is about 3 times larger than the observation, so called the cosmological $^7$Li problem. The $^7$Li abundance strongly depends on the $^7$Be production. The $^7$Be$(n, p)^7$Li reaction is considered as the main process to destroy $^7$Be during the BBN. Although its resonance structure has been well investigated, the contribution of the transition to the first excited state of $^7$Li at the BBN energies ($\sim$25 keV--1 MeV) has never been discussed. The $^7$Be$(n,\alpha)^4$He reaction might be the second important $^7$Be destroyer, but its experimental reaction rate has not been investigated until the recent studies, which yet involve uncertainty in the BBN energy region. We performed indirect measurements of these reactions simultaneously by the Trojan Horse Method (THM) at Center for Nuclear Study Radioactive Ion Beam (CRIB) separator. This study is one of the first attempts to apply the THM to RI+n reactions together with a recent collaborating study led by L. Lamia and the INFN-LNS nuclear astrophysics group. The experimental setup consisted of two parallel-plate avalanche counters to track the $^7$Be RI beam, a CD$_2$ target, and six ∆E-E position-sensitive silicon telescopes to observe the $^7$Be$(d, ^7$Li$p)^1$H and $^7$Be$(d, \alpha \alpha)^1$H reactions in inverse kinematics, which allows us to approach the $^7$Be$(n, p)^7$Li and $^7$Be$(n, \alpha)^4$He reactions in quasi-free kinematics, respectively. We aimed to resolve both the ground and the first excited states of $^7$Li by Q-value spectrum of the 3-body reactions for the first time. We observed several thousands of valid events in quasi-free kinematics. Some results including the Q-value spectrum, the momentum distribution of the spectator, and the preliminary cross sections of the $^7$Be$(n, p)^7$Li and the $^7$Be$(n, \alpha)^4$He reactions will be presented.

Speaker: Seiya Hayakawa

Slides S.Hayakawa-OMEG2017.pdf

26 The effects of time-dependent non-thermal distribution on the lithium problem of BBN

Aiming to resolve the so called lithium problem, we investigate the possibility that a small fraction of primordial particles can have non-thermal distribution for a short period of time of the BBN evolution. Our model is described by four parameters, which account the amount of fraction, the position and the width of time for the appearance of the particles, and the shape of the non-thermal distribution. By scanning the four-dimensional parametric space of wide range, we can find a set of points that give us a good agreement with the observational data including the primordial lithium abundance. Aspects of those solutions will be discussed.

Speaker: Tae-Sun Park (Sungkyunkwan University)

Coffee break

Session 8 (Chair: C. H. Hyun)

27 Collective neutrino oscillations

Collective oscillations of neutrinos represent emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. The symmetries of the problem in the full three flavor mixing scheme and in the exact many-body formulation by including the effects of CP violation and neutrino magnetic moment will be discussed. The connection between neutrino collective oscillations and the dynamics of core-collapse supernovae and the origin of chemical elements will be elucidated.

Speaker: Akif Baha Balantekin (U.of Wisconsin)

28 Nucleosynthesis and neutrinos in compact binary mergers

The merger of binary neutron stars or a neutron star and a black hole can eject an amount of 0.001-0.1 solar mass of neutron-rich matter after the merger. The rapid neutron capture process (r-process) is expected to occur in these ejecta and may be responsible for the electromagnetic transient called kilonova or macronova, which is an important counterpart of the future gravitational wave detection. Due to the evolution of the system after merger, various components of ejecta via different ejection mechanisms, such as the tidal force, shock heating, viscosity, and neutrinos, can give rise to distinct features in terms of their r-process nucleosynthesis outcome and the resulting kilonova/macronova light curve. I will discuss these aspects based on our recent works of studying the r-process nucleosynthesis of different evolutionary phases [1,2], the impact of theoretical nuclear physics inputs [1,2], the potential observational consequences [3,4], and the challenging neutrino physics [5]. [1] J. Mendoza-Temis et. al., PRC 92 (2015) 055805. [2] M.-R. Wu et. al., MNRAS 463 (2016) 2323. [3] J. Barnes et. al., ApJ 829 (2016) 110. [4] S. Rosswog et. al., Class. Quantum Grav. 34 (2017) 104001. [5] M.-R. Wu et. al., arXiv:1701.06580.

Speaker: Meng-Ru Wu

Slides M.Wu-OMEG2017.pdf

29 The evolution of very massive stars

In the work, we are going to discuss the stellar evolution of Very Massive Stars (M>100 Mo) in different metallicities. This includes the general properties, impact on the chemical abundances due to the rotational impact, dependences in metallicities and mass loss of very massive stars. Very massive stars has very large convective core during the main sequence thus their evolution do not affected by rotational mixing but by the mass loss due to the stellar winds. In the work we also going to discuss the one of the rate of VMS, the pair instability supernovae where we modeled PISN from our VMS progenitor models.

Speaker: Norhasliza Yusof (U. of Malaysia)

Symposium Lunch

Session 9 (Chair: S. C. Yang)

30 Determining nucleosynthesis yields in supernovae from spectral modelling

Supernovae are the main production factories of the elements in the Universe. Elements are created both during the hydrostatic burning phases of the progenitor star, and in the explosion. For many decades this framework has relied solely on theoretical predictions, but lately spectral synthesis models as well as improved supernova data availability has allowed direct abundance measurements. I review the picture we have today on supernova nucleosynthesis from spectral analysis, and implications for our understanding of both supernovae and the origin of the elements.

Speaker: Anders Jerkstrand

Slides A.Jerkstrand-OMEG2017.pdf

31 Abundance matching, galaxy sizes, and the Tully-Fisher relation in EAGLE

The Tully-Fisher relation (TFR) has been interpreted as reflecting the mass-velocity scaling (M ∝ V^3 ) of dark matter halos, but this interpretation has been called into question by abundance-matching (AM) models. We study the TFR of luminous spirals and its relation to AM using the EAGLE set of ΛCDM cosmological simulations. Matching both relations requires disk sizes to satisfy constraints given by the concentration of halos and their response to galaxy assembly. EAGLE galaxies approximately match these constraints and show a tight mass-velocity scaling that compares favourably with the observed TFR. The TFR is degenerate to changes in galaxy formation efficiency and the mass-size relation; simulations that fail to match the galaxy stellar mass function may fit the observed TFR if galaxies follow a different mass-size relation. The small scatter in the simulated TFR results because, at fixed halo mass, galaxy mass and rotation speed correlate strongly, scattering galaxies along the main relation. EAGLE galaxies evolve with lookback time following approximately the prescriptions of AM models and the observed mass-size relation of bright spirals, leading to a weak TFR evolution consistent with observation out to z=1.

Speaker: Ismael Ferrero

32 Big bang nucleosynthesis, the CMB, and the origin of matter and space-time

This talk will summarize the application of BBN and the CMB to constrain the first moments of the creation of matter in the universe. One expects that the universe was born out of complicated landscape near the Planck time. In these moments the energy scale of superstrings was obtainable during the early moments of chaotic inflation. This talk explores the possibility that a specific superstring excitation may have made itself known via its coupling to the field of inflation. This may have left an imprint of "dips" in the power spectrum of temperature fluctuations in the cosmic microwave background. The identification of this particle as a superstring is possible because there may be evidence for different oscillator states of the same superstring that appear on different scales on the sky. It will be shown that from this imprint one can deduce the mass, number of oscillations, and coupling constant for the superstring. Although the evidence is marginal, this may constitute the first observation of a superstring in Nature. At the same time, the existence of extra dimensions during inflation impacts the tensor to scalar ratio and the running spectral index. We summarize how the constraints on inflation shift when embedded in higher dimensions. Finally, higher dimensions also impact the cosmic expansion through the projection of curvature from the higher dimension in the "dark radiation" term. We summarize current constraints from BBN and the CMB on this brane-world dark radiation term.

Speaker: Grant Mathews

Coffee break

Session 10 (Chair: S.-C. Yoon)

33 Supernova nucleosynthesis

Supernova nucleosynthesis had been studied in 1-dimensional and multi-dimensional numerical simulations. I briefly summarize the supernova nucleosynthesis with results of the 1-dimensional simulations because essences of supernova nucleosynthesis are kept and easily understood. Products of supernova nucleosynthesis have clues to constrain origin of metal-poor stars and supernova explosion mechanisms. I introduce several elements which possess important information on them. Furthermore, I mention formation mechanisms of second-generation stars after supernova explosions of first stars.

Speaker: Nozomu Tominaga

Slides N.Tominaga-OMEG2017.pdf

34 Nuclear physics uncertainties in nucleosynthesis of s- and p-nuclei

Even in nucleosynthesis processes involving nuclei at or close to stability, not all reaction rates are experimentally constrained. In addition, even with the presence of measurements, these are often not able to fully constrain the stellar reaction rate due to thermal population of excited target states in the stellar plasma or bear large error bars. From a theory point of view, certain nuclear properties, such as gamma-strength functions or optical potentials, have to be predicted. These problems introduce sometimes considerable uncertainties in the predicted yields, in addition to uncertainties stemming from the astrophysical modelling. A short overview of the currently prevailing nuclear uncertainties and attempts for future improvements in the framework of the compound and direct reaction mechanisms is given. To guide future improvements in measurements and theoretical models it is necessary to quantify the total uncertainties introduced in the final isotopic yields by the conspiration of all combined individual uncertainties and to identify the reaction mostly contributing to a given uncertainty. A versatile Monte Carlo tool has been developed to address this question. It allows the simultaneous variation of thousands of reaction rates within their individually assigned error bars. This tool is being applied to study a number of nucleosynthesis scenarios and to quantify the nuclear uncertainties appearing within them. As examples, results are presented for the gamma-process and the weak s-process in massive stars and the main s-process in intermediate mass stars. Elemental and isotopic uncertainties are shown and key reactions identified.

Speaker: Thomas Rauscher

35 On understanding nuclear reaction network flows wih branchings on directed graphs

A nuclear reaction flow, appropriately scaled, gives the number of nuclei of a particular species undergoing a particular reaction per unit time. Such information provides important clues as to how nuclei are synthesized in an astrophysical environment and which nuclear reactions govern the resulting yields. For example, reaction flows in the s process of nucleosynthesis show the main reaction pathway as well as the key branchings. Reaction flows become less diagnostic when then are no longer unidirectional. For example, in explosive nucleosynthetic environments, reaction flows in one direction are often nearly balanced in the reverse. One can discuss net flows in such cases, but the overall nuclear flow dynamics are complicated and difficult to follow. Here I describe how consideration of branchings on directed graphs can aid understanding of reaction flows in explosive nucleosynthesis. I illustrate the utility of branchings with examples from alpha-constrained quasi-equilibrium and freeze out of the r-process of nucleosynthesis.

Speaker: Bradley Meyer

Slides B.Meyer-OMEG2017.pdf

36 Multi-dimensional simulations of core-collapse supernova explosions with CHIMERA

Unraveling the core-collapse supernova (CCSN) mechanism is problem that remains essentially unsolved despite more than four decades of effort. Spherically symmetric models with high physical fidelity generally fail to produce explosions, and it is widely accepted that CCSNe are inherently multi-dimensional. Progress in realistic modeling has occurred recently through the availability of petascale platforms and the increasing sophistication of supernova codes. We will discuss our most recent work on understanding neutrino-driven CCSN explosions employing multi-dimensional neutrino-radiation hydrodynamics simulations with the CHIMERA code. We discuss the inputs and resulting outputs from these simulations, the role of neutrino radiation transport, and the importance of multi-dimensional fluid flows in shaping the explosions.

Speaker: Bronson Messer

Poster session (Chair: K. Cho)

3 min. talks by poster presenters

37 Effects of sterile neutrino and extra-dimension on big bang nucleosynthesis

By assuming the existence of extra-dimensional sterile neutrinos in the early universe, we investigate the sterile neutrino effects on the big bang nucleosynthesis (BBN) and constrain some parameters associated with the sterile neutrino properties. First, for cosmic expansion rate, we take into account effects by a five-dimensional bulk and intrinsic tension of the brane embedded in the bulk, and constrain a key parameter on the extra dimension by the observational element abundances. Second, effects of the sterile neutrino traveling on or off the brane are considered. In this model, the effective mixing angle between the sterile and an active neutrino depends on energy, which may give rise to a resonance effect on the mixing angle. Consequently, reaction rate of the sterile neutrino can be drastically changed during the cosmic evolution. We estimated abundances and temperature of the sterile neutrino by solving the rate equation as a function of temperature until decoupling of the sterile neutrino and found that the relic abundance of the sterile neutrino is maximized for a characteristic resonance energy. Finally, some constraints related to the sterile neutrino, mixing angle and mass difference, are discussed in detail with the comparison of our BBN calculations corrected by the extra-dimensional sterile neutrino to observational data on light element abundances.

Speaker: Dukjae Jang

38 $\beta$-decay scheme of $^{140}$Te to $^{140}$I: Suppression of Gamow-Teller transitions between the neutron $h_{9/2}$ and proton $h_{11/2}$ doublet orbitals

In astrophysical environments, the beta($\beta$)-decay of unstable nuclei plays a crucial role in generating the final isotopic abundances along with rapid neutron-capture reactions (r-processes). The $\beta$-decay strengths are largely influenced by the so-called Gamow-Teller (G-T) interaction that is closely related to the spin-isospin interaction. This spin-isospin excitation is one of important ingredient for modeling the nuclear shell structure. Consequently, the role played by the G-T transition provides plenty of information on nuclear structure and nucleosynthesis. The G-T strength has been mainly constrained by the transformation between a proton and a neutron in the high-angular momentum orbital-spin partners such as; $\pi f_{7/2}$-$\nu f_{7/2}$, $\pi g_{9/2}$-$\nu g_{9/2}$, and $\pi h_{11/2}$-$\nu h_{11/2}$. However, in extreme neutron-rich environments, it can be controlled by the interplay between a neutron in the upper orbital and a proton in the lower orbital among a spin-orbital doublets, for instance, $\pi h_{11/2}$-$\nu h_{9/2}$. Investigating of the neutron-rich nuclei beyond $^{132}$Sn has attracted much attention because they are expected to reveal changes of size, diffuseness, and shell closures and, on the other side, to give information on nucleosynthesis along the r-process paths. However, it is a challenging task to determine decay rates and life times for the nuclei in this region. Here we present for the first time the $\beta$-decay of $^{140}$Te ($Z=52$) to odd-odd $^{140}$I ($Z=53$). The parent nuclide $^{140}$Te was produced through the in-flight fission of $^{238}$U beam with the energy of 345 MeV per nucleon on a $^{9}$Be target at the Radioactive Ion Beam Factory (RIBF), RIKEN. By using a $\beta$-delayed $\gamma$-ray spectroscopy, a decay scheme of $^{140}$I has been established. Three levels fed strongly from the ground 0$^{+}$ state of the mother nucleus $^{140}$Te have been assigned as a 1$^{+}$ state based on the log$ft$ values. These 1$^{+}$ states can be interpreted as being associated with the $\pi h_{11/2}$$\nu h_{9/2}$ configuration formed by the G-T transition between a neutron in the $h_{9/2}$ orbital and a proton in the $h_{11/2}$ orbital. Systematic features of level structures and G-T transitions are discussed within the framework of the spherical shell model and deformed shell model descriptions.

Speaker: Byul Moon

39 Development of a position-sensitive ionization chamber for astrophysical measurements

Intensity monitoring and particle identification of beams and beam-like heavy recoils can improve the accuracy of a cross section measurement in nuclear astrophysics. A gas-filled ionization chamber is still well-suited for this purpose due to its sturdiness against radiation damage and relatively good energy resolution. To overcome the maximum counting rate of about 100,000 pps for conventional ionization chamber, a new fast response ionization chamber with multi-electrodes was developed at the Sungkyunkwan University. By adopting two position-sensitive anodes, the position information of the incident charged particle could be obtained as well. The results of off-line tests using alpha emitting source and future plan of commissioning will be presented.

Speaker: Minsik Kwag

40 18Ne(α,α)18Ne scattering measurement for study on astrophysically-important 22Mg nuclide

The 18Ne(α,p)21Na reaction, one of the breakout reactions from hot-CNO cycle, plays a crucial role in understanding the X-ray bursts and the nucleosynthesis in the rp-process. Because this reaction rate is dominated by the energy levels of 22Mg above the α-threshold at 8.14 MeV, studying the 22Mg nuclide may improve our understanding of the X-ray burst. In order to study the level properties in 22Mg nuclide, the 18Ne(α,α)18Ne scattering reaction was measured in inverse kinematics by using radioactive 18Ne beams and 4He gas cell target at the Center for Nuclear Study Radioactive Ion Beam Separator (CRIB) in RIKEN Nishina center. By adopting thick-target method, the energy levels in 22Mg ranging from ~8.5 MeV to 18 MeV were populated. Details of the experiment and the preliminary results will be discussed in this presentation.

Speaker: Soomi Cha

41 The production of 98Tc through the neutrino process in supernova explosion

The star which the end is core collapse supernova, emit amount of neutrinos in this process. While these neutrinos pass through each layer of the star, they react with the nuclides of the star. We consider that because the origin of some elements are explained mostly by this neutrino process. One of that kinds of element is 98Tc. We checked that the contribution of reactions related to 98Tc neutrino reactions.

Speaker: Heamin Ko

Slides H.Ko-OMEG2017.pdf

42 Pre-supernova models for massive stars produced with large nuclear reaction network by MESA

Supernova (SN) is one of violent phenomena in the universe. SN generates heavy elements and leaves neutron star behind. It has been known that the physical properties of SN depend on those of pre-supernova such as mass, metallicities including distribution of elements, and the density and temperature profile which are obtained from the stellar evolution calculation. In particular, the production of heavy elements in SN is sensitive to the abundance profiles in the pre-supernova models. In this study, we evolved massive main sequence stars (Mstar>15Msun) by using large nuclear reaction networks that include heavy elements beyond iron. Our calculations were done by MESA (Modules for Experiments in Stellar Astrophysics) which allowed us to use networks containing a few hundred isotopes. We discuss how to select an effective network with the limited number of isotopes for the explosive nucleosynthesis of heavy elements in SN.

Speaker: Byeongchan Park

Slides B.Park-OMEG2017.pptx

43 Simulating X-ray bursts with a radiation hydrodynamics code

Previous simulations of X-ray bursts, for example, those performed by MESA (Modules for Experiments in Stellar Astrophysics) could not address the dynamical effects of strong radiation, which are important to explain the photospheric radial expansion (PRE) phenomena seen in many XRBs. In order to study the effects of strong radiation, we use SNEC (the SuperNova Explosion Code), a 1D Lagrangian open source code that is designed to solve hydrodynamics and equilibrium-diffusion radiation transport together. Because SNEC is able to control modules of radiation-hydrodynamics for properly mapped inputs, radiation-dominant pressure occurring in PRE X-ray bursts can be handled. Here we present simulation models for PRE XRBs by applying SNEC together with MESA.

Speaker: Gwangeon Seong

44 Linear proportional relationship between N(OH) and N(CH) in the diffuse interstellar medium

It has been known that there is a linear proportional relationship between the column densities of CH and OH measured toward bright UV-emitting stars, although there are four outliers in this relationship among the total 24 measured targets. We investigate reasonable configurations of diffuse interstellar medium (ISM) which could explain the observed relationship by considering the followings. First, we identify the locations of 24 targets on the celestial sphere and find that some targets gather together. By using the Simbad database, we count the number of molecular clouds, nebulae, and peculiar stars toward the targets which could contribute to the production of OH and CH. We also search carbon and oxygen line spectra toward 19 targets whose distances were measured in order to find correlation between two molecules and two atoms. We present the results of our search and test a few hypothetical configurations of diffuse ISM which may explain the observed relationship.

Speaker: SeungYeong Hong

45 Study of the 18F(p,a)15O reaction and the structure of 19Ne using a radioactive 15O beam

The gamma-rays emitted from novae are mainly due to e+-e- annihilation, and the positrons are mostly from the beta decay of 18F. The amount of 18F in nova is determined by two reaction channels of 18F(p,a)15O and 18F(p,γ)19Ne. The 18F(p,a)15O reaction is known as the main destruction channel, and it also affects the reaction rate for calculating the type I x-ray burst model. For this reason, the resonance parameters in 19Ne above the proton threshold at Ex =6.411MeV play an important role to understand the 18F(p,a)15O reaction. Many experiments and theoretical works have been reported on 19Ne resonance states. However, many relevant parameters are still ambiguous. The alpha elastic scattering experiment was performed at the Center for Nuclear Study Radioactive Ion Beam Separator(CRIB). The 7MeV/u 15N primary beam from the AVF cyclotron bombarded a H2 gas target to produce a 15O radioactive beam, which in turn reacted with a 600 Torr He gas target. By detecting alpha particles using the deltaE-E silicon telescopes, the alpha elastic scattering on 15O was investigated using the thick target method in inverse kinematics for studying the structure of 19Ne. The scanned energy range of 19Ne was Ex=3.53~11.13MeV. The experimental details and the results on the structure of 19Ne and the 18F(p,a)15O reaction will be presented.

Speaker: Dahee Kim

46 Constraining feedback prescriptions with Lyman-alpha absorption around galaxies

Understanding the physics of the gas present in galactic halos and spread among galaxies is of primary importance to get insight into galaxy formation and to address the open questions about the epoch of reionization. In particular, outflows of gas produced by stellar feedback (e.g. supernovae, stellar winds) or an AGN alter the physical state of gas in the circum- and intergalactic media (CGM and IGM) surrounding galaxies, although the details of these processes are still poorly understood. The nature of such processes can be unveiled exploiting Lyman-alpha absorption, which is a formidable tool to probe IGM and CGM. We use the state-of-the-art Illustris and Nyx hydrodynamic cosmological simulations to reproduce the observations of the Lyman-alpha absorption due to neutral hydrogen extending from 20 kpc up to several Mpc around foreground star-forming galaxies, quasars, and damped Lyman-alpha absorbers (DLAs), illuminated by a background quasar. We find that both simulations do not produce enough absorption within the virial radius to match the observations. Outside the virial radius up to ~1 Mpc, Nyx and Illustris yield very different predictions of the Lyman-alpha absorption. We assert that such differences could be ascribed to the diverse feedback prescriptions in the two simulations. Nevertheless, both simulations are consistent with currently available data within the error bars. Thus, improving the precision of measurements of Lyman-alpha absorption in the CGM with future observations, thanks to JWST and surveys like DES, has a great potential to constrain feedback prescriptions in numerical simulations. We show that the discrepancy can be due to the presence of cooler gas in the CGM, extra turbulence in the CGM, or unresolved physics in the CGM.

Speaker: Daniele Sorini

47 $^{26m}$Al beam production and decay measurement at CRIB

Nuclear isomers are commonly known and discussed, yet the term is difficult to define precisely. Generally, isomers are excited states in nuclei showing significantly different lifetimes compared to nearby states owing to various structural anomalies. Their existence in astrophysical environments leads to fascinating intricacies in the production of elements which might otherwise be difficult to probe. $^{26}$Al has been observed in the Milky Way, but its production is complicated by a low-lying isomer, $^{26m}$Al, which has zero spin and thus a short lifetime $T_{1/2} = 6$ s compared with its ground state which lives $0.7 Myr$ and is $5^{+}$. These species can mix and come into equilibrium when exposed to a hot proton bath such as a unique route to shed light on these physics. We performed the production and characterization of a $^{26m}Al$ beam at CTIB facility in 2016, which was then successfully used in a subsequent scattering measurement. We present a comparison of the obtained decay data of $^{26m}$Al with a detailed GEANT4 simulation, which we are applying to extract the isomer content of our in-flight radioactive beam.

Speaker: Hideki Shimizu

48 Poster session ( ~ 18:40)

Friday, 30 June

Session 11 (Chair: T. Ahn)

49 Progress of mass measurements of short-lived nuclides at the heavy-ion storage in Lanzhou

Speaker: Yuhu Zhang

Slides Y.Zhang-OMEG2017.pdf

50 Progress of nuclear astrophysics and underground project in China

Jinping Underground laboratory for Nuclear Astrophysics (JUNA) project takes the advantage of the ultra-low background of CJPL lab, high current accelerator and highly sensitive detectors to directly measure a number of crucial reactions occurring at their relevant astrophysical ener- gies. In current phase, JUNA aims at the direct measurements of 25Mg(p,γ)26Al, 19F(p,α)16O, 13C(α,n)16O and 12C(α,γ)16O reactions. The progress, including experimental setup, accelerator system, detector development, and low background test, will be presented.

Speaker: Weiping Liu

51 Present status of the KISS project

KISS project aims at finding an astrophysical condition for synthesizing r-process heavy elements, which form the third peak in the solar abundance pattern. This is an experimental challenge in nuclear physics to measure ground and isomeric state properties of unknown nuclei around the region of N=126 isotones. So far we have constructed and developed new type of mass separation system, KISS (KEK Isotope Separation System) and performed measurements of lifetimes and hyperfine structures of some platinum and iridium neutron-rich radioactive isotopes by applying multi-nucleon transfer reactions and in-gas laser ionization and spectroscopy methods. In this report, I will present recent physics results, updated KISS performance, and future’s research plan including systematic mass measurements with MRTOF (Multi-Reflaction Time-Of-Flight spectrograph).

Speaker: Hiroari Miyatake

Slides H.Miyatake-OMEG2017.pdf

Coffee break

Session 12 (Chair: C.-H. Lee)

52 Elastic $\alpha$-$^{12}$C scattering at low energies in cluster effective field theory

The elastic α-$^{12}$C scattering at low energies is studied employing an effective field theory in which the α and $^{12}$C states are treated as elementary-like fields. We discuss scales of the theory at stellar energy region that the $^{12}$C(α, γ)$^{16}$O process occurs, and then obtain an expression of the elastic scattering amplitudes in terms of effective range parameters. Using experimental data of the phase shifts for l=0,1,2 channels at low energies, for which the resonance regions are avoided, we fix values of the parameters and find that the phase shifts at the low energies are well reproduced by using three effective range parameters for each channel. Furthermore, we discuss problems and uncertainties of the present approach when the amplitudes are extrapolated to the stellar energy region.

Speaker: Shung-Ichi Ando

53 Neutron removal from deformed 31Ne

Experimental data on Coulomb breakup and neutron removal indicate that 31Ne is the heaviest halo driven by deformation. The possible ground state of 31Ne is either 3/2- or 1/2+. To study the neutron removal from 31Ne, we use a knockout model with deformed single-particle wave functions and investigate the deformation effects on cross sections and longitudinal momentum distributions. Our numerical analysis shows a preference for the 31Ne ground state with spin-parity 3/2-.

Speaker: Juhee Hong

54 \nu\bar\nu-pair and axion productions in strong magnetic field in relativistic quantum approach and cooling of magnetars

Magnetic fields in neutron stars play an important role in the interpretation of many observed phenomena. Magnetar, which is associated with a super strong magnetic field, show properties different than normal neutron stars. Particularly large luminosity of photon and neutrino emission attract attention from many researchers. In this work we study new cooling processes of magnetars, {$\nu {\bar \nu}$}-pair and axion productions from the transition between the different Landau levels for electron and proton, which occur only under the strong magnetic field. In the strong magnetic field the quantum calculation is necessary because production ratios are often much larger than those in the semi-classical and/or perturbative calculations [1]. We have found that the temperature dependences in the {$\nu {\bar \nu}$}-pair and axion production processes are much weaker than those of the usual processes such as the modified Urca (MU) and direct Urca (DU), and that the emission ratio becomes much larger than those with the MU an DU processes in the low temperature region below 1keV. [1] T.Maruyama et al., Phys. Rev. D91, 123007 (2015);, Phys.Lett.B757, 125 (2016).

Speaker: Tomoyuki Maruyama

55 Dark matter research cluster based on computational science

Theoretical and experimental studies have been consistently performed to find the undiscovered substances that make up the dark matter. Let me introduce the convergence research cluster for dark matter supported by National Research Council of Science and Technology. Dark matter researchers are in the process of forming a network based on computational science to establish the foundation for cooperative research. The current role and plan will be discussed.

Speaker: Kihyeon Cho

Lunch break

Session 13 (Chair: K. Kwak)

56 Supernova signatures in polar ice cores

Gamma rays, X-rays and UV radiation arising from solar activity and supernova explosions in our galaxy cause changes in the chemical composition of the stratosphere from ~10 - 50 km altitude. The effect of radiation on the stratosphere is then recorded in the chemical composition of terrestrial ice. The effect observed in the ice cores which we have obtained from the Dome Fuji research station in Antarctica is much greater than the effects observed in any of the ice cores that have been studied in the northern and southern hemispheres (e.g., Fourré et al., 2006; Motizuki et al., 2017). In this presentation, we discuss one possible source of yearly-scale peaks that are present in nitrate ion (NO3-) concentration profiles with a temporal resolution of about 1 year in a shallow Dome Fuji ice core drilled in 2001. It will be emphasized that the yearly-scale peaks, not being on a weekly-scale, cannot be attributed to solar proton events (e.g., McCracken et al., 2001); nor, being on a daily-scale, can the yearly-scale peaks be related to a depositional process (Wolff et al., 2008). We consider here galactic supernova explosions, and diagnose our yearly-scale NO3- peaks with respect to data precision, reproducibility, coincidence with other anionic and cationic events, uncertainties in ice-core dating, and possible contamination. We also consider the amount and duration of gamma-ray emissions from a galactic supernova, the effects on chemical reactions induced in the stratosphere, and the energetics of the production of nitrogen oxides by gamma-ray emissions from galactic supernova explosions compared with production by solar UV radiation. Since several NO3- concentration peaks are almost coincident with the dates of galactic supernova explosions that have occurred in the last millennia, we propose that the yearly-scale NO3- concentration peaks in ice cores drilled at Dome Fuji station be treated as a candidate proxy for supernova explosions that have occurred in our galaxy.

Speaker: Yuko Motizuki

57 Neutrino process with primitive meteorites and high power laser

A huge number of neutrinos emitted in core-collapse supernova explosions (neutrino process) play an important role in stellar nucleosyntheses of rare some nuclides such as Li-7, Be-11, F-19, Nb-92, La-138, and Ta-180. The study of the neutrino process can contributes to estimation of neutrino energy spectra and explosion mechanism. In the mass region heavier than iron, only three nuclides are known as the neutrino isotopes. If we can find other candidates for neutrino production, it helps to constrain precisely the neutrino energy spectra emitted from proto-neutron stars. We have proposed the neutrino-induced reaction production of an unstable isotope of Tc-98 with a half-life of 4.2 Myr. We calculate its abundance with a supernova model coupled with calculated neutrino induced reaction cross sections involved. A key input for the calculation of the neutrino process is destruction rates by photodisintegration reactions on excited nuclei at high temperature environments. We have proposed direct measurements of photon-induced reaction cross sections on nuclei excited by high power laser to simulate stellar environments.

Speaker: Takehito Hayakawa

58 Indirect studies on astrophysical reactions at the low-energy RI beam separator CRIB

CRIB (CNS Radioisotope Beam Separator) is a low-energy RI beam separator operated by CNS, University of Tokyo, located at RIBF of RIKEN Nishina Center. Various experimental projects based on interests for nuclear astrophysics have been carried out at CRIB, forming international collaborations. We present recent activities on nuclear astrophysics at CRIB. We have studied proton/alpha resonant scatterings on many systems [1,2], using thick target method in inverse kinematics. We observed nuclear resonances which may contribute to astrophysical reaction rates. As for the 7Be+a resonant scattering [2], we evaluated 7Be(a,g) resonant reaction rate with the higher-lying resonance information obtained with the measurement. The latest resonant scattering measurement was the proton resonant scattering on an isomer-enriched 26Al RI beam. Indirect measurements of relevant astrophysical reactions have also been performed at CRIB. The world’s first application of the Trojan horse method for an RI beam was to determine the astrophysical 18F(p,alpha) reaction rate. We measured quasi-free 18F(d,alpha n) reaction and determined the low-temperature 18F(p,alpha) reaction S-factor for the first time [3]. Another measurement was performed recently to determine 7Be(n,p) and (n,a) reaction rates, which can be relevant for the cosmological 7Li abundance problem. References [1]　J.J. He et al., Phys. Rev. C 88, (2013) 012801(R). [2] H. Yamaguchi et al., Phys. Rev. C 87 (2013) 034306. [3] S. Cherubini et al., Phys. Rev. C 92 (2015) 015805.

Speaker: Hidetoshi Yamaguchi

Coffee break

Session 14 (Chair: S. C. Kim)

59 Exotic structures in the nuclear dipole spectrum

Electric-dipole resonances in nuclei, and in particular exotic nuclei, have been linked theoretically to important phenomena on vastly different scales: they facilitate nucleosynthesis processes, especially when they lie close to the particle emission threshold; and through their properties we hope to learn about neutron skins and the nuclear symmetry energy, a key factor in the evolution of neutron stars. I plan to discuss recent progress and new opportunities in understanding the richness of the dipole excitation spectrum, based on microscopic calculations and how they compare with existing data on stable and exotic nuclei [1-3]. I will focus on the influence of shell structure and of loosely bound orbitals on low-energy transition strength, particularly relevant near the drip lines [1,2]. I will take the opportunity to briefly present theoretical advances based on realistic two- and three-nucleon interactions [4,5]. [1] P.Papakonstantinou et al., Phys. Lett. B 709 (2012) 270; Phys. Rev. C 89 (2014) 034306; Phys. Rev. C 92 (2015) 034311 [2] Y.Kim and P.Papakonstantinou, Eur. Phys. J. A 52 (2016) 176 [3] V.Derya et al., Phys. Lett. B 730 (2014) 288 [4] P.Papakonstantinou and R.Roth, Phys. Lett. B 671 (2009) 356 [5] P.Papakonstantinou, R.Trippel, R.Roth, Acta Phys. Pol. B 48 (2017) 527 Related to topics : Theoretical nuclear physics for astrophysics ; next generation RI beam facilities ; nuclear matter and neutron stars

Speaker: Panagiota Papakonstantinou

Slides P.Papakonstantinou-OMEG2017.pdf

60 Heavy ion fusion reactions in stars

Heavy ion fusion reactions play important roles in a wide variety of stellar burning scenarios. For example, ${}^{12}$C+${}^{12}$C, ${}^{12}$C+${}^{16}$O and ${}^{16}$O+${}^{16}$O are the principle reactions during the advance burning stages of massive star. ${}^{12}$C+${}^{12}$C also triggers the happening of superburst and Type Ia supernovae. The heavy ion fusion reactions of the neutron-rich isotopes such as ${}^{24}$O are the major heating source in the crust of neutron star. In this talk, I will review the challenges and the recent progress in the study of these heavy ion fusion reactions at stellar energies. The outlook for the studies of the astrophysical heavy-ion fusion reactions will also be presented.

Speaker: Xiaodong Tang

Slides X.Tang-OMEG2017.pdf

Concluding session (Chair: M.-K. Cheoun)

61 Concluding remarks

Speaker: Toshitaka Kajino