Directly Detecting MeV-Scale Dark Matter Via Solar Reflection.

Haipeng An,Adam Ritz,Maxim Pospelov,Josef Pradler

doi:10.1103/physrevlett.120.141801

Abstract

If dark matter (DM) particles are lighter than a few MeV/c^{2} and can scatter off electrons, their interaction within the solar interior results in a considerable hardening of the spectrum of galactic dark matter received on Earth. For a large range of the mass versus cross section parameter space, {m_{e},σ_{e}}, the "reflected" component of the DM flux is far more energetic than the end point of the ambient galactic DM energy distribution, making it detectable with existing DM detectors sensitive to an energy deposition of 10-10^{3} eV. After numerically simulating the small reflected component of the DM flux, we calculate its subsequent signal due to scattering on detector electrons, deriving new constraints on σ_{e} in the MeV and sub-MeV range using existing data from the XENON10/100, LUX, PandaX-II, and XENON1T experiments, as well as making projections for future low threshold direct detection experiments.

Highlights

If dark matter (DM) particles are lighter than a few MeV=c2 and can scatter off electrons, their interaction within the solar interior results in a considerable hardening of the spectrum of galactic dark matter received on Earth
A well-motivated class of models achieves the required relic abundance through thermal freeze-out during the early radiation-dominated epoch, which points to particles with weak-scale interactions—weakly interacting massive particles (WIMPs)—with the required annihilation rate hσannvi ∼ 10−36 cm2 (c 1⁄4 1 on)
This has motivated efforts to extend this reach to lower mass scales that still allow for viable thermal relic DM candidates, often with interactions mediated by new light forces [9]

Summary

Introduction

If dark matter (DM) particles are lighter than a few MeV=c2 and can scatter off electrons, their interaction within the solar interior results in a considerable hardening of the spectrum of galactic dark matter received on Earth. After numerically simulating the small reflected component of the DM flux, we calculate its subsequent signal due to scattering on detector electrons, deriving new constraints on σe in the MeV and sub-MeV range using existing data from the XENON10/100, LUX, PandaX-II, and XENON1T experiments, as well as making projections for future low threshold direct detection experiments.

Results

Conclusion