A Universal Bound on QCD Axions from Supernovae

TL;DR

This paper introduces a new supernova-based production channel for QCD axions, providing the strongest model-independent constraints on axion mass by leveraging a novel shift-symmetry-breaking operator.

Contribution

It identifies a previously unconsidered axion production mechanism in supernovae, leading to significantly improved bounds on axion properties independent of specific models.

Findings

New axion production channel in supernovae identified

Stronger, model-independent bounds on axion mass established

Improvement over previous constraints by two orders of magnitude

Abstract

We identify a new production channel for QCD axions in supernova environments that contributes to axion emissivity for all models solving the strong CP problem. This channel arises at tree-level from a shift-symmetry-breaking operator constructed at next-to-leading order in Chiral Perturbation Theory. In scenarios where model-dependent derivative couplings to nucleons are absent, this sets the strongest model-independent constraint on the axion mass, improving on existing bounds by two orders of magnitude.