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

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 ($16660\pm 270$) kg$\cdot$day. 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 $1.14\times 10-44$ cm$2$ 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 $\sim 100$ 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-$\sigma$ detection of supernova neutrinos out to a distance of $\sim 20$ kpc, covering the entire Milky Way Galaxy. Argo can make a 5-$\sigma$ detection out to a distance of $\sim 40$ 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.