Study of core-collapse supernovae : New experimental constrains on the nuclear physics inputs

Simon Giraud, Michigan State University
Thursday, Feb 20, 11:00 AM - Research Discussion
1200 FRIB Laboratory

Abstract:  To model the composition of the core of a massive star during its collapse, a treatment of the nuclear statistical equilibrium, starting from a single-nucleus approximation equation of state (Lattimer and Swesty, LS), has been built recently. This allows a more realistic description of the nuclear distribution inside the core and, more specifically, to quantify the role of the nuclear masses. The distributions obtained with the original mass functional (LS) and those obtained with HFB-24 and DZ10 mass models have been compared for several thermodynamic conditions of a typical CCSN trajectory. The differences in the composition could lead up to approximately 25% deviations in the electron-capture rate, thus showing the need to identify a proper mass model to use in CCSN simulations. Therefore, new high precision mass measurements in the nuclear mass region of interest, via a double Penning trap at the IGISOL facility (Jyvaskyla, Finland), were performed. Five new mass excess were determined for the following nuclei : 69m,70Co, 74,75Ni and 76mCu. The precision has been improved for five others : 67Fe, 69Co, 76,78Cu and 79mZn. The experimental values of the nuclear gaps for Z=28 and N=50 have been compared with the results predicted by DZ10 and HFB-24. The latter model better reproduces the evolution of these gaps. Despite the different predictions of DZ10 and HFB-24, a moderated impact of the mass model on the composition of the collapsing core was found after implementing the recent statistical treatment in an existing CCSN hydrodynamical simulation. Moreover, those differences in composition have a small effect on the collapse dynamics, which appears to be more sensitive to the electron-capture model. The latter can be better constrained by means of nuclear charge exchange experiments. The upcoming 14O(d,2He)14N charge exchange experiment using the AT-TPC should demonstrate a very promising way of constraining the electron capture rates of the exotic nuclei capturing the most during the CCSN.