Dark Side Doesn't Find Dark Matter Either

The DarkSide-50 direct dark matter detection experiment bridges most of the mass gap between LZ and XENONnT experiment dark matter searches previously discussed. 

A trio of papers report that it too has not seen any signal of dark matter, greatly constraining the parameter space of any dark matter candidates that interact with ordinary matter even much weaker than that of a neutrino.

We report on the search for dark matter WIMPs in the mass range below 10 GeV/c^2, from the analysis of the entire dataset acquired with a low-radioactivity argon target by the DarkSide-50 experiment at LNGS. The new analysis benefits from more accurate calibration of the detector response, improved background model, and better determination of systematic uncertainties, allowing us to accurately model the background rate and spectra down to 0.06 keV(er). A 90% C.L. exclusion limit for the spin-independent cross section of 3 GeV/c^2 mass WIMP on nucleons is set at 6×10^−43 cm^2, about a factor 10 better than the previous DarkSide-50 limit. This analysis extends the exclusion region for spin-independent dark matter interactions below the current experimental constraints in the [1.2,3.6] GeV/c^2 WIMP mass range.

The DarkSide-50 Collaboration, "Search for low-mass dark matter WIMPs with 12 ton-day exposure of DarkSide-50" arXiv:2207.11966 (July 25, 2022).

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 (12306 ± 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.

The DarkSide-50 Collaboration, "Search for dark matter-nucleon interactions via Migdal effect with DarkSide-50" arXiv:2207.11967 (July 25, 2022).

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 (12306 ± 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 g(Ae), 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 sterile neutrinos.

The DarkSide-50 Collaboration, "Search for dark matter particle interactions with electron final states with DarkSide-50" arXiv:2207.11968 (July 25, 2022).