Low-Energy Physics in Liquid Argon Time Projection Chambers

Abstract

The Deep Underground Neutrino Experiment (DUNE) will be at the frontier of neutrino physics. However, its goals require unprecedented calibrations of charge, light readout, and the detector electric field. Especially for the subcomponents exposed to an intense neutrino beam. Particles traversing liquid argon time projection chambers (LArTPCs) leave behind wakes of ionization electrons. DUNE, whose main components are LArTPCs, will image the topologies of these wakes with ~ 0.5 cm precision and ~500 ns timing resolution and, based on the kinematics, identify the particle species and interaction types. In other words, DUNE will conduct precision neutrino physics. This thesis is a calibration and a study of ~ 10 - 100 MeV electromagnetic interactions in LArTPCs. Although DUNE will be sensitive to a wide range of energies, this work focuses on the low end. Also, this thesis is a calibration of LArTPC electric fields. At the MeV scale, DUNE will be sensitive to solar, supernova, and perhaps even exotic neutrinos. However, this sensitivity rests squarely on detector calibrations. This thesis examines ~ 10 MeV and 236 MeV with measured delta-rays and simulated anomalous kaon decay-at-rest (KDAR) neutrinos respectively. I show that the ~ 10 MeV response differs from predictions by < 10%. This is very encouraging for neutrino astronomy. I also show that DUNE will be sensitive to very low anomalous neutrino fluxes from the Sun. This is exciting for testing dark matter models which can be linked to neutrinos. This work also measures the spatial offsets (at the ~ mm level) due to electric field distortions in DUNE prototypes, highlighting possible defects and the need for meticulous field characterization for future LArTPCs.