Nuclei in the Cosmos (NIC XVII)

Insight to the Explosion Mechanism of Core Collapse Supernovae Through γ-ray Spectroscopy of 46Cr

19 Sept 2023, 18:25

5m

Poster Core-collapse supernovae, mergers and the r-process Poster session (Core-collapse supernovae, mergers and the r-process)

Speaker

Christopher COUSINS (University of Surrey)

Description

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.