Probing sub-GeV Dark Matter with conventional detectors

TL;DR

This paper introduces a novel method for detecting sub-GeV Dark Matter by utilizing inelastic photon emission during nuclear recoil, enabling new constraints on low-mass Dark Matter with existing detectors.

Contribution

It proposes using photon emission in nuclear recoil to overcome kinematic detection limits for low-mass Dark Matter, setting first constraints below 500 MeV.

Findings

First limits on Dark Matter below 500 MeV established

Photon emission enables detection of low-mass Dark Matter

Bremsstrahlung as a detection channel for suppressed Dark Matter-electron coupling

Abstract

The direct detection of Dark Matter particles with mass below the GeV-scale is hampered by soft nuclear recoil energies and finite detector thresholds. For a given maximum relative velocity, the kinematics of elastic Dark Matter nucleus scattering sets a principal limit on detectability. Here we propose to bypass the kinematic limitations by considering the inelastic channel of photon emission in the nuclear recoil. Our proposed method allows to set the first limits on Dark Matter below 500 MeV in the plane of Dark Matter mass and cross section with nucleons. In situations where a Dark Matter-electron coupling is suppressed, Bremsstrahlung may constitute the only path to probe low-mass Dark Matter awaiting new detector technologies with lowered recoil energy thresholds.