Search for Dark Matter and Neutrino Events with the Darkside Liquid Argon Time Projection Chambers



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Many astronomical observations found that atomic matter can account for only a small fraction of the matter in the Universe. Evidences from cosmology show that dark matter must be non-baryonic. Weakly interacting massive particles (WIMPs) is a leading candidate for dark matter. Searching for WIMPs has become a major activity of particle physics.

DarkSide-50 did a search for WIMPs using a liquid argon time projection chamber (LAr TPC) with low-radioactivity underground argon (UAr). Null result was reported by DarkSide-50 for a 532-day data collection, corresponding to an exposure of (16660±270) kgday. At the best sensitivity, for WIMP mass around 100 GeV, a 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section of 1.14×10−44 cm2 was derived.

Research on particle identification using machine learning techniques in DarkSide-50 data analysis is presented. Both supervised and unsupervised learning algorithms were developed. Monte Carlo simulation was used to generate training data for supervised learning. A greater power of suppressing ER backgrounds at ∼100 PE was achieved. The unsupervised learning uses DarkSide-50 experimental data for training, whose result needs to be validated with more analysis.

DarkSide-20k and Argo are the next two generations of LAr TPCs for WIMP searches, having an active mass of 38.6 and 400 tonnes, respectively. In these larger detectors, neutrinos become an irreducible background for WIMP searches. This dissertation presents a calculation of the neutrino event rate in the DarkSide-20k LAr TPC.

A study on supernova neutrino detection with DarkSide-20k and Argo is presented. DarkSide-20k can make a 5-σ detection of supernova neutrinos out to a distance of ∼20 kpc, covering the entire Milky Way Galaxy. Argo can make a 5-σ detection out to a distance of ∼40 kpc. It is demonstrated that DarkSide-20k and Argo can measure the total energy emitted and average neutrino energy to a precision of a few percent, as well as significantly detect the neutronization burst out to great distances.



Dark matter, Neutrinos, LAr TPC, Supernova Neutrinos