Bounds on Axions-Like Particles Shining in the Ultra-Violet

TL;DR

This paper uses ultraviolet data from the Hubble Space Telescope to set new constraints on axion-like particles in the multi-eV mass range, significantly improving previous limits on their coupling to photons.

Contribution

It provides the first constraints on ALPs in the 14.4-22.2 eV mass range using UV observations, surpassing previous bounds by over an order of magnitude.

Findings

Excluded ALP-photon couplings above 10^{-12} GeV^{-1} in the 14.4-22.2 eV mass range.

Used archival Hubble data of dwarf galaxies and galaxy clusters.

Set new limits on ALPs in the ultra-violet spectrum.

Abstract

Axion-like particles (ALPs) can decay into two photons with a rest-frame frequency given by half of the ALP mass. This implies that ultra-violet searches can be used to investigate ALPs in the multi-eV mass range. We use archival data from the Hubble Space Telescope between 110 and 170 nm to constrain ALPs with mass between 14.4-22.2 eV. We consider observations of a set of dwarf spheroidal galaxies and galaxy clusters and assume the ALP density in these objects to follow their dark matter density. The derived limit on the ALP-photon coupling $g_{a\gamma}$ excludes values above $10^{-12}~{\rm GeV}^{-1}$ over the whole mass range and surpasses previous limits by over one order of magnitude.