The Darkside-20k Dark Matter Detector

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The detection of galactic dark matter and the establishment of its fundamental properties are a very high priority in particle physics. The most sensitive direct searches for high mass WIMP (weakly interacting massive particle) dark matter use large liquid noble gas detectors to search for nuclear recoils.Our objective is a program in liquid argon to reach down in sensitivity to the "Neutrino Floor" caused by atmospheric neutrinos coherently scattering in the detector and generating recoils that simulate WIMP dark matter. This objective has resulted in the joining together of all the argon dark matter researchers in the world, to form a global argon dark matter collaboration.Our current detector, called "DEAP--3600", contains about 3.3 tonnes of liquid argon, is situated in SNOLAB,  and is currently the most sensitive argon dark matter detector in the world. The light emission properties of liquid argon have already been demonstrated in DEAP to enable discrimination greater than 108 against other backgrounds such as radon and solar neutrinos at the Neutrino Floor.  This proposal is requesting support to enable Canadian researchers to participate in the "Darkside--20k" detector, a large liquid argon time projection chamber(TPC) that will be situated in the Gran Sasso Laboratory in Italy that will extend the reach of liquid argon dark matter detection by an order of magnitude. Canadian groups have started to work on several aspects of the DarkSide--20k program, particularly in areas where they have strong past experience: the silicon-photomultiplier data acquisition system and electronics, the underground argon plant and subsequent storage and processes, the design of the detector, the unique TPC to be built from acrylic in Canada, and the procedures to fabricate and coat acrylic with resistive coatings for TPC components and with TPB for wavelength shifting. The main capital costs associated with these activities have been requested in a separate CFI proposal, with a total value of $22M. DarkSide-20k will have ultra-low backgrounds that can be measured in situ. This will give sensitivity to WIMP--nucleon cross sections of 1.2 x 10--47 cm2(1.1 x 10-46 cm2) for WIMPs of 1 TeV/c2 (10 TeV/c2) mass, to be achieved during a 5 year run producing an exposure of 100 tonne--year free from any instrumental background. After the experiment in Italy is complete, the plan is to build an even larger detector of 400 tonnes (Argo) that will be located at the SNOLAB underground laboratory in Sudbury.  .