Probing photophobic axion and relaxion dark matter

Abstract

We investigate the interplay between early universe cosmology and dark matter direct detection, considering axion models with naturally suppressed couplings to photons. In the context of the cosmological relaxation of the electroweak scale, we focus on a scenario of relaxion dark matter, in which the relaxion field constitutes all the observed dark matter relic density and its allowed mass range is fixed to a few keV by construction. In particular, we show that a relaxion particle with mass ${m}_{\\ensuremath{\\phi}}=3.0\\text{ }\\text{ }\\mathrm{keV}$ which couples to electrons with ${g}_{\\ensuremath{\\phi},e}=6.8\\ifmmode\\times\\else\\texttimes\\fi{}{10}^{\\ensuremath{-}14}$ is consistent with the XENON1T excess, while accounting for the observed dark matter and satisfying astro/cosmo probes. This scenario uses the electroweak scale as the link connecting the relaxion production at early times with the dark matter absorption rate in direct detection.