Impact of Nucleon-Nucleon Bremsstrahlung Rates Beyond One-Pion Exchange

TL;DR

This study investigates how modern nuclear interaction-based nucleon-nucleon bremsstrahlung rates affect supernova neutrino emission and proto-neutron star cooling, revealing modest impacts despite significant rate reductions.

Contribution

It introduces a new approach using modern nuclear interactions for bremsstrahlung rates, improving upon the traditional one-pion-exchange approximation in supernova models.

Findings

Neutrino luminosities change by less than 5%.

Average neutrino energies increase by up to 0.7 MeV.

Proto-neutron star cooling slows by less than 1 second.

Abstract

Neutrino-pair production and annihilation through nucleon-nucleon bremsstrahlung is included in current supernova simulations by rates that are based on the one-pion-exchange approximation. Here we explore the consequences of bremsstrahlung rates based on a modern nuclear interactions for proto-neutron star cooling and the corresponding neutrino emission. We find that despite a reduction of the bremsstrahlung emission by a factor of 2-5 in the neutrinospheric region, models with the improved treatment exhibit only $\lesssim$5% changes of the neutrino luminosities and an increase of $\lesssim$0.7 MeV of the average energies of the radiated neutrino spectra, with the largest effects for the antineutrinos of all flavors and at late times. Overall, the proto-neutron star cooling evolution is slowed down modestly by $\lesssim$0.5-1 s.