DarkSide-20k and the Future Liquid Argon Dark Matter Program

Abstract

DarkSide ran since mid 2015 a 50-kg-active-mass dual-phase Liquid Argon Time Projection Chamber (TPC), filled with low-radioactivity argon from an underground source and produced world class results for both the low mass (MW I M P below 20 GeV/c2) and high mass (MW I M P above 100 GeV/c2) direct detection search for dark matter. The next stage of the DarkSide program will be a new generation experiment, called DarkSide-20k, involving a global collaboration formed by members of the main current argon-based experiments. DarkSide-20k, is designed as a 20-tonne fiducial mass dual-phase Liquid Argon TPC with SiPM-based cryogenic photosensors, and is expected to be free of any instrumental background for an exposure of >100 t · yr. Like its predecessor, DarkSide-20k will be housed at the INFN Gran Sasso underground laboratory (LNGS), and it is expected to attain a WIMP-nucleon cross section 90% C.L. exclusion sensitivity of 7.4×10-48cm2 for a WIMP mass of 1 TeV/c2 in a 200 t · yr run. DarkSide-20k will be installed inside a membrane cryostat containing more than 700 t of liquid argon, and be surrounded by an active neutron veto based on a Gd-loaded acrylic shell. The article will give the latest updates of the ongoing R&D and prototype tests validating the initial design. A subsequent objective, towards the end of the next decade, will be the construction of the ultimate detector with a 300 t fiducial mass, Argo, to push the sensitivity to the neutrino floor region for high-mass WIMPs.