Assessing the Relative Importance of Neutrino–Matter Interaction Channels in post-merger remnant of neutron star mergers

The emission and absorption of neutrinos via weak interactions have significant impacts on the thermodynamics and composition evolution of the post-merger remnant of neutron star mergers. Current simulations of the neutrino transport equations employ approximations in the transport algorithm and neutrino-matter interaction rates. This alters our ability to meticulously analyze kilonovae signals and the relative contribution of the merger ejecta to the nucleosynthesis of different heavy elements. The addition of new reactions into merger simulations based on detailed calculations of interaction rates is a cumbersome process. To help prioritize future work in this area, we seek to evaluate the relative importance of different neutrino-matter interactions. To this end, the current study analyzes relative reaction rates from standard charged current, elastic and inelastic scattering reactions and pair processes on 3D snapshots at regular time intervals of a SpEC merger simulation using the NuLIB library and an energy-dependent Monte-Carlo radiation transport algorithm. Further, we compare the impact of relaxing the assumptions of equilibrium neutrino distribution for pair processes and elastic scattering. Finally, we look at the energy spectrum of neutrinos in the simulations and assess the impact of the use of equilibrium spectra in gray transport schemes.