Speaker
Description
DarkSide-20k is a direct dark-matter detection experiment which is under construction underground at LNGS. It deploys a 50 tonne dual-phase liquid-argon TPC designed for nearly instrumental background-free operation. DarkSide-20k is projected to probe spin-independent dark matter-nucleon scattering down to 7.4 x 10-48 cm2 for a 1 TeV/c2 dark matter candidate, approaching the neutrino floor. This talk focuses on the low-mass regime, where sensitivity reach is governed by detector thresholds and by the high-velocity tail of the local dark-matter phase-space distribution. Within an ionisation-only (S2-only) analysis framework, we quantify the impact of an LMC (Large Magellanic Cloud)-perturbed halo model on DarkSide-20k sensitivity, demonstrating that changes to the high-speed tail can affect projections in threshold-limited regions. Nuclear-recoil induced atomic ionisation (the Migdal effect) is incorporated as an additional electronic channel, to extend sensitivity below the conventional nuclear-recoil threshold and into the sub-GeV mass range.
Given the resulting enhanced sensitivity, an extended DarkSide-20k null result would imply exceptionally strong exclusions. We therefore perform a complementary, decision-relevant study: conditioning on a DarkSide-20k null, we assess the probability that next-generation detectors beyond achieve a 5σ discovery. We construct a likelihood-based inference that maps DarkSide-20k outcomes to a posterior over particle-physics parameters, and propagate this posterior through forward models of future experiments to evaluate their conditional discovery probabilities. This provides a quantitative metric for whether additional detector generations are expected to retain meaningful discovery potential once DarkSide-20k constraints are taken into account.