Low-mass inelastic dark matter direct detection via the Migdal effect

Understand

We consider searches for the inelastic scattering of low-mass dark matter at direct detection experiments, using the Migdal effect.

• We find that there are degeneracies between the dark matter mass and the mass splitting that are difficult to break.
• Using XENON1T data we set bounds on a previously unexplored region of the inelastic dark matter parameter space.
• For the case of exothermic scattering, we find that the Migdal effect allows xenon-based detectors to have sensitivity to dark matter with ${\cal O}(\mathrm{MeV})$ mass, far beyond what can be obtained with nuclear recoils alone.