Pion mass effects on axion emission from neutron stars through NN bremsstrahlung processes

TL;DR

This paper calculates axion emission rates from nucleon-nucleon bremsstrahlung in neutron stars, incorporating pion mass effects, revealing significant temperature-dependent corrections that impact axion mass constraints.

Contribution

It introduces a comprehensive calculation of axion emission rates including full momentum contributions from one pion exchange, improving upon previous models.

Findings

Finite momentum corrections significantly affect emissivities in non-degenerate regimes.

Nuclear effects tend to decrease axion emission rates.

Results suggest revisions to existing axion mass bounds.

Abstract

The rates of axion emission by nucleon-nucleon bremsstrahlung are calculated with the inclusion of the full momentum contribution from a nuclear one pion exchange (OPE) potential. The contributions of the neutron-neutron (nn), proton-proton (pp) and neutron-proton (np) processes in both the nondegenerate and degenerate limits are explicitly given. We find that the finite momentum corrections to the emissivities are quantitatively significant for the non-degenerate regime and temperature-dependent, and should affect the existing axion mass bounds. The trend of these nuclear effects is to diminish the emissivities.