Probing the axion-photon coupling: phenomenological and experimental perspectives. A snowmass white paper

TL;DR

This paper reviews current and future experimental and astrophysical searches for axions and axion-like particles via their coupling to photons, highlighting recent bounds and prospects for detecting dark matter axions.

Contribution

It provides a comprehensive overview of phenomenological and experimental approaches to probing axion-photon coupling, including astrophysical bounds, helioscopes, and haloscopes.

Findings

Astrophysical bounds limit axion-photon coupling from stellar energy loss.

Helioscopes search for solar axions converting into X-rays in magnetic fields.

Haloscopes aim to detect galactic dark matter axions.

Abstract

We present a brief overview of the ongoing searches for the axion particle via its coupling to photons. Both the classical QCD axions and more recently proposed Axion-Like-Particles are considered. Astrophysical bounds on the axion-photon coupling come from considerations of stellar energy loss during Helium burning, in both low- and high-mass stars. Helioscopes look for back-conversion of solar axions into x-ray photons in strong laboratory magnetic fields. Finally, haloscopes aim to detect dark matter axions in our galactic halo. Both types of searches are expecting significant advances in the future, which will enable them to probe large, well-motivated parts of the parameter space below the stellar cooling bounds.