Supernova limits on 'QCD axion-like particles'

TL;DR

This paper investigates how supernova observations constrain the properties of QCD axion-like particles, especially their couplings to nucleons and photons, significantly narrowing the viable parameter space for these particles.

Contribution

It provides new astrophysical bounds on ALP-nucleon couplings for masses above 1 MeV, extending previous constraints and linking high-energy theories to low-energy observables.

Findings

Supernova data exclude ALP-nucleon couplings down to 10^{-11} for masses above 1 MeV.

ALPs with masses greater than 1 MeV can decay into photons, affecting astrophysical signals.

The study narrows the parameter space for QCD ALPs, impacting future searches.

Abstract

In this paper, we explore the phenomenology of massive Axion-Like Particles (ALPs) coupled to quarks and gluons, dubbed 'QCD ALPs', with an emphasis on the associated low-energy observables. ALPs coupled to gluons and quarks not only induce nuclear interactions at scales below the QCD-scale, relevant for ALP production in supernovae (SNe), but naturally also couple to photons similarly to the QCD-axion. We discuss the link between the high-energy formulation of ALP theories and their effective couplings with nucleons and photons. The induced photon coupling allows ALPs with masses $m_a\gtrsim1$ MeV to efficiently decay into photons, and astrophysical observables severely constrain the ALP parameter space. We show that a combination of arguments related to SN events rule out ALP-nucleon couplings down to $g_{aN}\gtrsim 10^{-11}- 10^{-10}$ for $m_a\gtrsim1$ MeV - a region of the parameter space that was hitherto unconstrained.