Galactic Origin of Relativistic Bosons and XENON1T Excess

TL;DR

The paper investigates whether relativistic bosons from dark matter decay or annihilation in our galaxy could explain the XENON1T excess, concluding current bounds prevent this explanation under existing constraints.

Contribution

It establishes model-independent upper bounds on relativistic boson fluxes from galactic dark matter and assesses their inability to account for the XENON1T excess within current experimental limits.

Findings

Galactic dark matter decay/annihilation cannot produce enough relativistic bosons to explain the XENON1T excess.

Derived upper bounds on boson fluxes are independent of boson identity or couplings.

Current experimental constraints prevent relativistic bosons from explaining the XENON1T anomaly.

Abstract

We entertain the exotic possibility that dark matter (DM) decays or annihilations taking place in our galaxy may produce a flux of relativistic very weakly-coupled bosons, axions or dark photons. We show that there exist several upper bounds for this flux on Earth assuming generic minimal requirements for DM, such as a lifetime longer than the age of the Universe or an annihilation rate that leaves unaffected the background evolution during matter domination. These bounds do not depend on the identity or the couplings of the bosons. We then show that this new flux cannot be large enough to explain the recent XENON1T excess, while assuming that the bosons' couplings to the Standard Model are consistent with all current experimental and observational constraints. We also discuss a possible caveat to these bounds and a route to explain the excess.