The recent electron recoil excess observed by XENON1T has a possible interpretation in terms of solar axions coupled to electrons. If such axions are still relativistic at recombination they would also leave a cosmic imprint in the form of an additional radiation component, parameterized by an effective neutrino number ΔNeff. We explore minimal scenarios with a detectable signal in future CMB surveys: axions coupled democratically to all fermions, axion-electron coupling generated radiatively, the DFSZ framework for the QCD axion. The predicted ΔNeff is larger than 0.03−0.04 for all cases, close to the 2σ forecasted sensitivity of CMB-S4 experiments. This opens the possibility of testing with cosmological observations the solar axion interpretation of the XENON1T excess.
@article{arxiv.2007.06579,
title = {Cosmic Imprints of XENON1T Axions},
author = {Fernando Arias-Aragon and Francesco D'Eramo and Ricardo Z. Ferreira and Luca Merlo and Alessio Notari},
journal= {arXiv preprint arXiv:2007.06579},
year = {2021}
}
Comments
8 pages, 4 figures. V2: references added, minor changes; version published in JCAP