Charged-current neutrino interactions in core-collapse supernovae in a virial expansion

Abstract

Core-collapse supernovae may depend sensitively on charged-current neutrino interactions in warm, low-density, neutron-rich matter. A proton in neutron-rich matter is more tightly bound than is a neutron. This energy shift $\Delta{U}$ increases the electron energy in $\nu_{e}+{n}\rightarrow{p}+{e}$, increasing the available phase space and absorption cross section. Likewise $\Delta{U}$ decreases the positron energy in $\bar\nu_{e}+{n}\rightarrow{p}+{e}^+$, decreasing the phase space and cross section. We have calculated $\Delta{U}$ using a model-independent virial expansion and we find that $\Delta{U}$ is much larger, at low densities, than the predictions of many mean-field models. Therefore $\Delta{U}$ could have a significant impact on charged-current neutrino interactions in supernovae. Preliminary simulations of the accretion phase of core-collapse supernovae find that $\Delta{U}$ increases $\bar\nu_{e}$ energies and decreases the $\nu_{e}$ luminosity.