The DarkSide Program for Direct Dark Matter Searches and Its Technologies for Liquid Argon Experiments

Titolo: The DarkSide Program for Direct Dark Matter Searches and Its Technologies for Liquid Argon Experiments

Relatore: Giuliana Fiorillo (Dipartimento di Fisica "Ettore Pancini" dell'Università degli Studi di Napoli "Federico II & INFN sez. Na)

Coordinate: martedì 3 maggio, ore 15:30, sala Azzurra LNS

Abstract: The DarkSide-50 dark matter detector at LNGS is a two-phase argon TPC, installed at the center of two nested veto detectors, a 30-tonne liquid scintillator neutron veto and a 1,000-tonne water Cherenkov muon veto.  While operating in 2014 with a fill of argon extracted from the atmosphere, DarkSide-50 demonstrated its capability to operate in a background-free mode even in presence of the strong radioactive background due to the 39Ar isotope produced by cosmic rays.  In 2015 DarkSide was filled with 150 kg of argon extracted from deep underground reservoirs, which was demonstrated to be highly depleted in 39Ar.  Today DarkSide-50 is the only noble liquid dark matter detector operating in background-free mode.

The combination of the DarkSide-50 results obtained with the atmospheric and underground argon fills allows to project that DarkSide-20k, a 20-tonne depleted argon detector proposed for construction at LNGS, will collect an exposure of 100 tonnes×year completely free of background. DarkSide-20k, set to start operating by 2020, will either detect WIMP dark matter or exclude a large fraction of the favored parameter space.

The future DarkSide program is made possible by special technological programs for the procurement of underground argon (Urania project), in its additional isotopic rejection of 39Ar (Aria project), and in the development of special SiPM to replace cryogenic PMTs for operation as photosensors at 87K.

This last development will be extensively tested by the ReD project, exposing a novel two-phase argon TPC instrumented with SiPM to monochromatic neutron beams. Using a closed kinematics approach, the ReD experiment will investigate the dependence of the LAr signal on the relative direction of the drift field relative to the initial momentum of the recoil. If this effect is large enough, it will open the way to a directional dark matter search using the DarkSide-20k with the potential to find conclusive evidence for dark matter or disprove the WIMP hypothesis at and above the mass range explored by planned accelerator experiments.