Shining dark matter in Xenon1T

TL;DR

This paper proposes that a 2 GeV dark matter particle interacting via Rayleigh operators could explain the Xenon1T electron recoil excess, with specific predictions for future detection signals.

Contribution

It introduces a novel dark matter interaction model involving higher dimensional Rayleigh operators to explain experimental anomalies.

Findings

Dark matter scattering produces keV photons mimicking electron signals.

Light mediators avoid indirect detection constraints.

Upcoming experiments may confirm or exclude the model.

Abstract

We point out that a non-relativistic $\sim 2 $ GeV dark matter (DM) which interacts with visible matter through higher dimensional Rayleigh operators could explain the excess of "electron recoil" events recently observed by the Xenon1T collaboration. A DM scattering event results in a few keV photon that on average carries most of the deposited energy, while the nuclear recoil energy is only a subleading correction. Since the Xenon1T detector does not discriminate between electrons and photons, such events would be interpreted as excess of the keV electrons. Indirect constraints from dark matter annihilation are avoided for light mediators of ${\mathcal O}(10~{\rm MeV})$ that have sizable couplings to neutrinos. One loop induced spin-independent scattering in dark matter may soon lead to a confirmation signal or already excludes regions of viable parameter space for the Rayleigh DM model, depending on what the exact values of the unknown nonperturbative nuclear matrix elements are.