Solar Neutrino Scattering with Electron into Massive Sterile Neutrino

TL;DR

This paper explores how solar neutrino scattering involving sterile neutrinos and light mediators can explain the Xenon1T excess, highlighting the role of sterile neutrino mass and different mediator types.

Contribution

It introduces the possibility of sterile neutrinos in explaining the Xenon1T excess via pseudoscalar mediators, which was previously considered unlikely.

Findings

Sterile neutrino final states can account for the Xenon1T excess.

A recoil energy lower bound indicates sterile neutrino mass presence.

Different mediators, including light Z', are briefly discussed.

Abstract

The recent Xenon1T excess can be explained by solar neutrino scattering with electron via a light mediator, either scalar or vector, in addition to many other explanations from the dark sector. Since only the recoil electron is observable, a keV sterile neutrino instead of an active neutrino can appear in the final state. The sterile neutrino allows pseudoscalar mediator to explain the Xenon1T excess which was thought impossible. In addition, nonzero recoil energy lower bound arises from the sterile neutrino mass, which can be used to testify if the sterile neutrino is massive or not. We also briefly discuss the case of a sterile neutrino final state with light $Z'$ mediator.