Light new physics in XENON1T

TL;DR

This paper explores whether new light scalar or vector mediators coupled to leptons could explain the low-energy electron recoil excess observed at XENON1T, highlighting the potential of dark matter detectors to probe new physics.

Contribution

It demonstrates that light mediators with masses below 50 keV could produce signals similar to the XENON1T excess, offering a novel way to test beyond Standard Model physics with dark matter detectors.

Findings

Scalar and vector mediators can mimic the XENON1T excess.

Dark matter detectors can compete with dedicated neutrino experiments.

Astrophysical constraints challenge the interpretation of the excess as new physics.

Abstract

We examine the recently-reported low-energy electron recoil spectrum observed at the XENON1T underground dark matter direct detection experiment, in the context of new interactions with solar neutrinos. In particular we show that scalar and vector mediators with masses $\lesssim 50$ keV coupled to leptons could already leave a visible signature in the XENON1T experiment, similar to the observed peak below 7 keV. This signals that dark matter detectors are already competing with neutrino scattering experiments such as GEMMA, CHARM-II and Borexino. If these results from XENON1T are interpreted as a new signal of such physics, the parameters which fit the excess face challenges from astrophysics which seem very difficult to overcome. If they are rather viewed as a constraint on new couplings, they herald the start of an era of novel precise probes of physics beyond the standard model with dark matter detectors.