Migdal ionization as a probe of light dark matter from Nuclear Transition

Abstract

Nuclear reactors serve as a key artificial source of light dark matter. Direct detection of reactor-produced dark matter faces substantial obstacles, since quenching effects suppress conventional elastic scattering signals below detector thresholds. We present a new search strategy utilizing the Migdal effect in germanium detectors to probe light dark matter produced via nuclear de-excitation from reactors. Using ON-OFF residual spectra from the TEXONO experiment, we set a new stringent limit on the dark matter and nucleus interaction over the mass range $0.01\,\text{MeV}\le m_χ\lesssim 2.6\,\text{MeV}$, which provides a complementary bound to existing cosmological and astrophysical limits.