Dissertation/Thesis Abstract

A Joint Analysis of T2K Beam Neutrino and Super-Kamiokande Sub-GeV Atmospheric Neutrino Data
by Li, Xiaoyue, Ph.D., State University of New York at Stony Brook, 2018, 200; 10844911
Abstract (Summary)

Neutrino oscillation is a phenomenon in which neutrinos produced from charged current weak interactions can change flavor as they propagate. The mixing between the three flavor eigenstates and mass eigenstates can be measured through neutrino oscillations as the oscillation probabilities depend on the mixing angles and neutrino mass squared differences.

T2K is a long baseline neutrino experiment, in which a nearly pure muon neutrino or muon antineutrino beam is produced at J-PARC on the east coast of Japan and travels 295 km through the Earth’s crust towards the far detector, Super-Kamiokande (Super-K), a 50 kiloton water Cherenkov detector, in the west of Japan. The neutrino fluxes in the absence of oscillation are measured by the near detectors 280 meters away from the target, and again with oscillation effects at Super-K. Aside from the beam neutrino from J-PARC, Super-K also measures neutrino oscillations independently through the neutrinos produced in the Earth's atmosphere.

This thesis presents the first analysis in which both the T2K beam neutrino data and the sub-GeV atmospheric neutrino data at Super-K are used in a unified framework to measure neutrino oscillation parameters. The beam neutrino samples are selected for optimal sensitivity to sin2&thetas;23 and δCP. A Bayesian analysis using a Markov Chain Monte Carlo method is performed. Using T2K Runs 1–8 data which amounts to 14.7 × 1020 protons on target (POT) in neutrino-mode and 7.6 × 1020 POT in antineutrino-mode, and 2520 days of Super-K data, the oscillation parameters are measured to be sin2&thetas; 23 = 0.528+0.032–0.028, |Δ m232| = 2.46+0.084 –0.060(10–3eV2), sin 2&thetas;13 = 0.0270+0.0065–0.0047 ; and the 90% credible interval of δCP is [–π, –0.18]&[2.33, π]. When the data is also combined with the constraint on sin2 2&thetas;13 = 0.0857 ± 0.046 from reactor neutrino experiments, the oscillation parameters are measured to be sin2&thetas;23 = 0.543+0.026 –0.023, |Δm2 32| = 2.49 +0.042–0.090(10–3eV2 ), sin2&thetas;13 = 0.0223+0.0012 –0.0013; the 90% credible interval of δ CP is [–π, –0.628], and the CP-conserving value δ CP = 0 is excluded at 2σ.

Indexing (document details)
Advisor: Jung, Chang Kee
Commitee: Karagiorgi, Georgia, McGrew, Clark, Shrock, Robert, Wilking, Michael
School: State University of New York at Stony Brook
Department: Physics
School Location: United States -- New York
Source: DAI-B 80/03(E), Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Physics, Particle physics
Keywords: CP-violation, Neutrino, Neutrino oscillations, Super-Kamiokande, T2K
Publication Number: 10844911
ISBN: 9780438572249
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