New limits on dark photons from solar emission and keV scale dark matter

Haipeng An,Josef Pradler,Maxim Pospelov,Adam Ritz

doi:10.1103/physrevd.102.115022

Abstract

We provide updates to the limits on solar emission of dark photons, or more generally any light vector particle coupled to the electron vector current. The recent 2019 and 2020 electronic recoil data from XENON1T now provides more stringent constraints on these models than stellar energy loss in the sub-keV mass region. We also show that solar emission of dark photons does not provide a good fit to the recent XENON1T excess in the 2-5 keV energy bins. In contrast, the absorption of 2-4 keV mass dark photons that saturate the local dark matter mass density does provide a good fit to the excess, for mixing angles in the range $\epsilon \in (4-12)\times 10^{-16}$, while satisfying astrophysical constraints. Similarly, other models utilizing the vector portal can fit the excess, including those with operators that directly couple the dark photon field strength to electron spin.

Highlights

The successful experimental program to scale up the size of underground dark matter detectors based on ultrapure xenon [1,2,3] has led to a range of significant new constraints on the properties of dark matter
We show that solar emission of dark photons does not provide a good fit to the recent XENON1T excess in the 2–5 keV energy bins
The primary goal of these experiments is the search for thermal relic weakly interacting massive particles (WIMPs) with a weak-scale mass, and the absence of clear signals has resulted in stringent constraints on the sub-weak-scale scattering cross sections with nuclei of any such models

Summary

INTRODUCTION

The successful experimental program to scale up the size of underground dark matter detectors based on ultrapure xenon [1,2,3] has led to a range of significant new constraints on the properties of dark matter. In comparison to underground experiments focused on neutrino detection, which are typically sensitive to energy depositions above a few hundred keV, xenon-based dark matter detectors provide the leading sensitivity for electronic energy depositions of 100 keV and below As they are large and very clean (i.e., almost free from radioactive contamination and external backgrounds), these experiments are at the forefront of searches for other exotic particles, beyond the familiar WIMP mass window. While the constraints on axionlike particles are generally weaker than those derived from astrophysics and stellar cooling, the limits on dark photons in the sub 10-eV mass range are competitive with the solar energy loss bounds. IV, we reach our conclusions and comment on generalizations of this analysis to the deexcitation of dark matter states

NEW BOUNDS ON SOLAR DARK PHOTONS

ABSORPTION OF keV-SCALE DARK MATTER AND THE XENON1T EXCESS

Findings

DISCUSSION