Search for Dark-Matter-Nucleon Interactions via Migdal Effect with DarkSide-50

Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c^{2} mass dark matter. We present new constraints for sub-GeV/c^{2} dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12 306±184)  kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40  MeV/c^{2}. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below 3.6  GeV/c^{2}.

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

We present a search for dark matter particles with sub-GeV/c^{2} 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[over ¯]_{e}, the axioelectric coupling constant g_{Ae}, and the dark photon kinetic mixing parameter κ. We also set the first dark matter direct-detection constraints on the mixing angle |U_{e4}|^{2} for keV/c^{2} sterile neutrinos.