ARGO - Development of next-generation argon dark matter search

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The dark matter problem has been around since the 1930's, since which time we have consistently found a significant excess of matter in galaxies or galaxy clusters beyond that explained by our observations of conventional matter, implying strongly that there exists a yet undiscovered form of matter that pervades the universe and far outweighs the conventional matter, by a factor of approximately 5 to 1. Direct observation of a dark matter particle would have strong implications for both astrophysics and particle physics. High-mass dark matter particles, for which the proposed experimental program has strong sensitivity, remain as very viable candidates in the search for dark matter. After the successful demonstration of argon as a dark matter target, the DEAP-3600 collaboration has joined in founding a new Global Argon Dark Matter Collaboration aimed at a phased approach towards an ultimate multihundred tonne argon detector for dark matter at SNOLAB, with ultimate sensitivity to the neutrino floor, defined by the region where backgrounds from neutrino interactions limit further sensitivity. The first step in that program is the DarkSide-20k (DS-20k) experiment, already under construction at LNGS in Italy, utilizing a sensitive target of 20 tonnes of argon, to be followed by the larger detector - ARGO. We are requesting here support for the early development of the ARGO concept. The research includes development of a detailed detector simulation and evaluation and evaluation of photodetector options to determine detector performance using wavelength-shifters (as all previous argon dark matter detectors have used), or using novel UV-sensitive photodetectors, as well development of a full detector background model. A strong component of the research includes the further development of novel and large-area 3D digital silicon photomultipliers, which are a crucial enabling component of the long-term argon dark matter program. This new technology, being pioneered by the research team, will revolutionize the detection of single photons, with broad applications that will allow improvements in not only astroparticle physics experiments, but also with a myriad of other potential scientific and commercial possibilities. It is strategically important to undertake early the study of the production and reliability of these devices, taking advantage of strong industrial ties in Canada, to ensure the required performance can be met. The proposed research also includes development related to the extraction of several hundred tonnes of low-radioactivity argon - an ultrasensitive assay system for the radioactive isotope 39Ar. The research program includes novel detector development, builds on existing investments and expertise, has strong ties to industrial partners and the over 400-member Global Argon Dark Matter collaboration. The research will lay the groundwork for the future experimental dark matter program, with strong opportunities for HQP training.