Xenon1T excess from electron recoils of non-relativistic Dark Matter

Dario Buttazzo,Paolo Panci,Daniele Teresi,Robert Ziegler

doi:10.1016/j.physletb.2021.136310

Abstract

We show that electron recoils induced by non-relativistic Dark Matter interactions can fit well the recently reported Xenon1T excess, if they are mediated by a light pseudo-scalar in the MeV range. This is due to the favorable momentum-dependence of the resulting scattering rate, which partially compensates the unfavorable kinematics that tends to strongly suppress keV electron recoils. We study the phenomenology of the mediator and identify the allowed parameter space of the Xenon1T excess which is compatible with all experimental limits. We also find that the anomalous magnetic moments of muons and electrons can be simultaneously explained in this scenario, at the price of a fine-tuning in the couplings of the order of a few percent.

Highlights

The Xenon1T collaboration has announced the results of a search for Dark Matter (DM) using electronic recoils with a 0.65 ton/years of exposure
While these interpretations have the advantage of not suffering from a lookelsewhere effect (LEE), essentially because their scale is fixed by the Sun temperature, they are strongly disfavored by astrophysical bounds [2,3]
Absorption of bosonic keV-scale DM or, in general, models where the keV scale is determined by kinematic features suffer of LEE and lower their statistical preference with respect to the Standard Model

Summary

Introduction

The Xenon1T collaboration has announced the results of a search for Dark Matter (DM) using electronic recoils with a 0.65 ton/years of exposure. The Xenon1T collaboration itself analyzed the signal in terms of solar axion absorption or solar neutrinos scattering off electrons with an enhanced magnetic moment While these interpretations have the advantage of not suffering from a lookelsewhere effect (LEE), essentially because their scale is fixed by the Sun temperature, they are strongly disfavored by astrophysical bounds [2,3]. While the scattering kinematics of non-relativistic DM tends to strongly suppress keV recoils (which are possible only in the momentum-distribution tails of the xenon atomic wave-functions), the interaction mediated by a pseudo-scalar increases with the exchanged momentum, partially compensating the unfavorable kinematics and allowing for a good fit of the excess. Signals that peak away from the threshold would not be explained by our model

KeV electron recoils from pseudoscalar mediator

Collider bounds

Possible UV completions

Discussion and conclusions