UC San Diego

We investigate neutral current neutrino-nucleus interactions of interest in the supernova problem: endothermic and exothermic inelastic neutrino scattering processes; de-excitation of hot nuclei into neutrino pairs; and neutrino-antineutrino annihilation processes involving nuclei. We employ a shell model based treatment including allowed and forbidden transitions to compute the relevant weak strength distributions in nuclei. We discuss Fermi gas fitting formulae for the differential cross sections of all four processes for use in numerical stellar collapse calculations. Since target nuclei in stellar collapse are expected to be in highly excited states we explicitly include thermal effects in our calculations. We find that low-energy neutrino-pair production from hot nuclei and exothermic neutrino-nucleus scattering may have an important role in determining the evolution of the lepton distribution functions in the infalling presupernova core.