Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.718812
Title: Cosmic ray background estimations in large liquid argon detectors for proton decay via p to K+ anti_nu and nu_e appearance from nu_mu beams
Author: Richardson, Martin
ISNI:       0000 0004 6349 0449
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Abstract:
In recent years caverns deep underground at Sanford Underground Research Facility (SURF) near Lead, SD, have been proposed to house a large-scale liquid argon detector. This was once intended to be part of the Deep Underground Science and Engineering Laboratory" (DUSEL) project to build extensive laboratory space for multidisciplinary scientific research, well-shielded from cosmic rays. The Long Baseline Neutrino Experiment" (LBNE) later proposed such a detector at SURF and in 2015 LBNE evolved into the Deep Underground Neutrino Experiment" (DUNE). All of these proposals have involved a detector suitable for the study of neutrino oscillation parameters, primarily using a nu_mu / anti_nu_mu beam generated at Fermilab in Batavia, IL. The large target mass also enables a nucleon decay search, as well as the study of other phenomena. Cosmic-ray muons are capable of penetrating deep below the surface of the Earth and causing events that mimic rare signal events. Monte Carlo simulations of the cosmic muon-induced background for proton decay via the channel p \rightarrow K+ anti_nu have been performed, where the signal is the observation of a single K+ track. Cuts have been developed to reject the background K+/K- observed, which has been estimated for a 10 kton (fiducial mass) LBNE/DUNE detector at a depth of 4850 ft and a 40 kton (fiducial mass) detector at 800 ft suitable for a DUSEL cavern. For the former the annual rate of background events for p \rightarrow K+ anti_nu after cuts is <2.3 * 10^{-3} kton^{-1} yr^{-1} (at 90% C.L.). For the latter this is <0.026 kton^{-1} yr^{-1}. The cosmic ray-induced background for nu_e appearance from the nu_mu beam has also been estimated for a near-surface level detector (10 kton fiducial mass) once proposed for LBNE. The signal in this instance is an electromagnetic (EM) shower. After cuts the background has been estimated as 2.88 +/- 0.25 yr^{-1} due to EM showers that start with gamma \rightarrow e+ e-. The upper limits of the annual rates of EM showers starting with K^0_L \rightarrow pi+/pi- e-/e+ anti_nu_e/nu_e in muon, proton and neutron-induced events are < 0.21 yr^{-1}, < 0.01 yr^{-1} and < 0.002 yr^{-1} (at 90% C.L.) after cuts. The upper limits of the annual rates of EM showers starting with pi0 \rightarrow e+ e- gamma in muon, proton and neutron-induced events are < 0.18 yr^{-1}, < 0.01 yr^{-1} and < 0.03 yr^{-1} (at 90% C.L.) after cuts.
Supervisor: Kudryavtsev, Vitaly Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.718812  DOI: Not available
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