Search for Dark Matter Particle Interactions with Electron Final States with DarkSide-50

We present a search for dark matter particles with sub-GeV/c2 masses whose interactions have final state electrons using the DarkSide-50 experiment's (12 306±184) kg d low-radioactivity liquid argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section σ¯e, the axioelectric coupling constant gAe, and the dark photon kinetic mixing parameter κ. We also set the first dark matter direct-detection constraints on the mixing angle |Ue4|2 for keV/c2 sterile neutrinos.