Chiral effective field theory description of neutrino nucleon-nucleon bremsstrahlung in supernova matter

We revisit the rates of neutrino pair emission and absorption from nucleon-nucleon bremsstrahlung in supernova matter using the T-matrix formalism in the long wavelength limit. Based on chiral effective field theory potentials, we solve the Lippmann-Schwinger/Bethe-Goldstone accounting for vacuum/in-medium and half-off-shell non-diagonal T-matrix elements, extending over previous calculations using the Born approximation. We compare our results with one pion exchange rates, commonly used in supernova simulations, and calculations using the effective on-shell T-matrix from measured phase shifts. We find rates enhanced by factors 2-3 for densities around 0.001/fm³, when compared with OPE results, and around 0.01/fm³, when compared with effective on-shell T-matrix results. At higher densities, final state blocking reduce the rates by around 30%. We also find that the impact of multi-scattering effects and RPA correlations are at the level of a few percent thus can be negligible.