Low-mass dark matter and neutrino-less double beta decay searches with tha darkside technology

The DarkSide program has delivered the first results on searches for dark matter with a target of ultra-pure low-radioactivity argon from underground sources (UAr) with the DarkSide-50 experiment, in operation at LNGS since 2013. The key element provided by the use of UAr is the strong reduction in activity of 39Ar relative to the atmospheric argon, which avoids the pile-up of events that would otherwise plague any argonbased events at the tonne scale and beyond. Thus the use of UAr enables the construction of very large scale dark matter detectors, able to combine the advantages of the unsegmented design and very strong rejection of electron recoils a↵orded by the pulse shape discrimination of liquid argon, thus able to probe the entire discovery space at high masses (>100 GeV/c2) prior to and through the onset of background from atmospheric neutrinos (the so called “neutrino floor”) in absence of any background from instrumental sources. The DarkSide Collaboration, which launched the DarkSide-50 program at LNGS, morphed to become the “Global Argon Dark Matter Collaboration” (GADMC). The GADMC started a program for the complete exploration of the discovery space of high-mass dark matter consisting of the DarkSide-20k experiment, at the scale of a few tens of tonnes, that is going to be constructed at LNGS and expected in operation by 2023, and Argo, at the scale of a few hundred tonnes, and proposed for installation at SNOLAB. The full exploitation of the UAr target for high-mass dark matter searches required the development of very special technologies. The GADMC developed special photodetector modules (PDMs) made of assemblies of silicon photomultipliers (SiPMs) and characterized by very high photon detection eciency, background much lower than traditional photomultiplier tubes (PMTs), and dark noise lower than that of PMTs when operated near a temperature of 87 K. The GADMC also developed a special plan for the high-throughput extraction of UAr at special gas wells in Colorado, USA, with the Urania plant and for its purification in the novel cryogenic distillation column Aria, characterized by the presence of thousands of equilibrium stages and currently under installation in a mine shaft in Sardinia, Italy. The Aria column with its unprecedented height may be able to provide further isotopic depletion in 39Ar of the UAr target. Exploration of high-mass dark matter is one of the main thrusts for the discovery of new physics beyond the standard model. In this dissertation, I will focus on the possible use of the DarkSide technology to tackle two di↵erent but equally crucial problems, which may also lead to new discoveries: the search for low-mass (<10 GeV/c2) dark matter and the search for the neutrinoless double beta decay