Dr Andreas Lohs
Neutrino-nucleon interactions at high density and temperature play a major role in the outcome of various processes during core-collapse supernovae (CCSNe) explosions. Their impact ranges from shock revival via neutrino heating to determining nucleosynthesis of heavy elements in the neutrino driven wind or via neutrino nucleosynthesis. Precise modelling of these scenarios requires accurate description of the underlying neutrino interaction rates, while at the same time adhering to computational constraints. In this context, we present a suitable method for precise calculations of neutrino mean free paths, for absorption and scattering type reactions. To be precise, we compute the exact Hartree response of nucleons (treating nucleons as quasi free fermions) for neutrinos, explicitely allowing for inelasticity, relativistic nucleons and massive leptons. We also discuss inclusion of the momentum transfer dependence of weak coupling constants. This approach is then compared to other computation methods for neutrino-nucleon interactions. In particular, we use it as a reference to asses the quality of various approximations for neutrino-nucleon interactions that are currently applied in CCSN simulations, such as the elastic approximation or analytic corrections for nucleon recoil and weak magnetism. This allows for a better understanding of the suitability of these approximations and for an estimation of the resulting uncertainties in the neutrino spectra of CCSNe.