Enhanced Supernova Axion Emission and its Implications

TL;DR

This paper calculates axion emission from thermal pions in supernovae and neutron star mergers, revealing higher emission rates and harder spectra than previously thought, which impacts astrophysical bounds and detection prospects.

Contribution

It introduces a new calculation of axion emission involving thermal pions, showing it exceeds nucleon-nucleon bremsstrahlung and affects axion mass bounds and detection strategies.

Findings

Axion emission rate is 2-5 times larger than previous estimates.

Axion spectrum is significantly harder, with higher energies.

Results imply stronger bounds on QCD axion mass and improved detection prospects.

Abstract

We calculate the axion emission rate from reactions involving thermal pions in matter encountered in supernovae and neutron star mergers, identify unique spectral features, and explore their implications for astrophysics and particle physics. We find that it is about 2-5 times larger than nucleon-nucleon bremsstrahlung, which in past studies was considered to be the dominant process. The axion spectrum is also found be much harder. Together, the larger rates and higher axion energies imply a stronger bound on the mass of the QCD axion, and better prospects for direct detection in a large underground neutrino detector from a nearby galactic supernova.