Search for Dark-Matter–Nucleon Interactions with a Dark Mediator in PandaX-4T

Abstract

We report results of a search for dark-matter--nucleon interactions via a dark mediator using optimized low-energy data from the PandaX-4T liquid xenon experiment. With the ionization-signal-only data and utilizing the Migdal effect, we set the most stringent limits on the cross section for dark matter masses ranging from $30\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ to $2\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$. Under the assumption that the dark mediator is a dark photon that decays into scalar dark matter pairs in the early Universe, we rule out significant parameter space of such thermal relic dark-matter model.