Plasma dark matter and electronic recoil events in XENON1T

TL;DR

This paper explores a dark plasma model with dark electrons and protons interacting via kinetic mixing, explaining the XENON1T electron recoil excess within astrophysical and experimental constraints.

Contribution

It introduces a plasma dark matter model with specific kinetic mixing parameters that can account for the XENON1T excess, aligning with existing constraints.

Findings

Dark electron scattering explains keV electron recoils.

Kinetic mixing parameter range consistent with observations.

Model compatible with astrophysical and cosmological constraints.

Abstract

Dark matter might be in the form of a dark plasma in the Milky Way halo. Specifically, we consider here a hidden sector consisting of a light `dark electron' and a much heavier `dark proton', each charged under an unbroken $U(1)'$ gauge symmetry. These self-interacting dark sector particles can also interact with ordinary matter via the kinetic mixing interaction, and lead to a signal in dark matter direct detection experiments. Indeed, keV electron recoils can arise quite naturally in such models from dark electron scattering off loosely bound atomic electrons. Here we examine the recently reported XENON1T excess in the context of such a plasma dark matter model. We find that the observed excess can be explained if kinetic mixing is in the approximate range: $10^{-12} \lesssim \epsilon \lesssim 10^{-10}$. The allowed parameter space is consistent with astrophysical and cosmological constraints and consistent also with other direct detection experiments.