Cosmic Ray Protons Illuminate Dark Matter Axions

TL;DR

This paper proposes a novel method to detect axion-like particles via photon emission from cosmic ray protons in axion fields, potentially constraining dark matter models with upcoming radio telescope observations.

Contribution

It introduces a new photon emission mechanism from cosmic rays in axion backgrounds and evaluates its detectability with the Square Kilometre Array.

Findings

Photon emission rate and spectrum computed for cosmic ray protons in axion fields.

Potential to constrain axion-like particle parameters with future radio observations.

Non-detection could set limits on ALP dark matter properties.

Abstract

Cosmic ray protons propagating in a spatially-homogeneous but time-dependent field of axions or axion-like particles (ALPs) emit photons in a way that is reminiscent of Cherenkov radiation by charged particles in a preferred background. We compute the emission rate and energy spectrum of the photons, and discuss the possibility of their detection using the Square Kilometre Array which is currently under construction. In the case of a non-detection, constraints can be placed on the parameter space of ALPs whose mass lie between $10^{-7}$eV and $10^{-5}$ eV under the assumption that they are the primary constituent of dark matter.