Probing Sub-GeV Dark Matter via Migdal Effect-Induced Electron Excitations

TL;DR

This paper explores how the Migdal effect can be used in superfluid helium detectors to detect very light dark matter particles down to a few MeV by observing electron excitations via UV-photon emission.

Contribution

It demonstrates a new detection channel using the Migdal effect in superfluid helium, extending sensitivity to sub-GeV dark matter.

Findings

Electron excitations via the Migdal effect can be observed in superfluid helium detectors.

The method allows probing dark matter masses as low as a few MeV.

Calculated event rates suggest enhanced sensitivity in direct detection experiments.

Abstract

The electron ionization predicted by the Migdal effect in dark matter-nucleus scattering enhances experimental sensitivity to sub-GeV dark matter. In this work, we demonstrate that lower-energy electron excitations provide a novel and promising pathway, enabling the detection of even lighter dark matter particles previously considered inaccessible for direct searches. Direct detection experiments employing a superfluid $^4$He target can exploit this channel by observing electronic excitations via UV-photon emission. We calculate the resulting event rates and find that electron excitations induced by the Migdal effect make it possible to probe dark matter-nucleus scattering for dark matter masses as small as a few MeV.