The axion-baryon coupling in SU(3) heavy baryon chiral perturbation theory

TL;DR

This paper extends the calculation of axion-baryon couplings from SU(2) to SU(3) heavy baryon chiral perturbation theory, revealing significant couplings to hyperons with implications for dense nuclear matter in astrophysics.

Contribution

It introduces the derivation of axion couplings to the full SU(3) baryon octet within heavy baryon chiral perturbation theory, expanding previous SU(2) analyses.

Findings

Axion also couples significantly to hyperons.

Results have implications for axion phenomenology in neutron stars.

Extension from SU(2) to SU(3) flavor symmetry.

Abstract

In the past, the axion-nucleon coupling has been calculated in the framework of SU(2) heavy baryon chiral perturbation theory up to third order in the chiral power counting. Here, we extend these earlier studies to the case of heavy baryon chiral perturbation theory with SU(3) flavor symmetry and derive the axion coupling to the full SU(3) baryon octet, showing that the axion also significantly couples to hyperons. As studies on dense nuclear matter suggest the possible existence of hyperons in stellar objects such as neutron stars, our results should have phenomenological implications related to the so-called axion window.