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Title: Study of neutrino-induced neutral current neutral pion production in the T2K near detector
Author: Short, Samantha
ISNI:       0000 0004 2742 0259
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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The T2K experiment is a long baseline neutrino oscillation experiment. The most intense accelerator muon neutrino beam ever built is produced at the J-PARC facility in Tokai, located on the east coast of Japan, and directed (2.5 [degrees] off -axis) toward the Super-Kamiokande water Cherenkov detector, located 295 km away in the mountains of western Japan. For the current T2K [Symbol appears here. To view, please open pdf attachment]e appearance analysis, 23% of the background at Super- Kamiokande is from neutral current interactions that produce one π0 in the final state (NC 1π0). This study uses ND280 Run 2 data totalling 7.832 x 10 [to the power of 19] POT and selects neutrino-induced NC 1π0 interactions in FGD1 and FGD2 where both π0 decay photons convert in the barrel and downstream ECAL. Overall, neglecting photon reconstruction efficiency, an efficiency of 22% and purity of 16% is obtained. For the case where both π0 decay photons convert in the downstream (barrel) ECAL an efficiency of 33% (12%) and purity of 43% (9%) is achieved. When one photon converts in the barrel ECAL and the other in the downstream ECAL the efficiency (purity) is 29% (16%). Systematic uncertainties arising from cross-section model parameters and final state interactions, the neutrino flux prediction and the shape discrepancy between ECAL variables in data and MC are evaluated. The predicted total number of events when both photons convert in the downstream and barrel ECAL is 7.1± 2.3 (syst)± 0.5 (stat) and 31.6± 8.9 (syst) ±1.2 (stat), respectively. Whereas when one decay photon is reconstructed in the barrel ECAL and the other in the downstream ECAL the expected number of events is 38.1± 8.7 (syst) ±1.3 (stat). The selected number of events in data is 5, 22 and 31, respectively, which agrees with the prediction within errors. The calibration of the time offsets for the barrel and downstream ECAL is also presented in this thesis. The application of this calibration reduces the timing resolution from 9 ns to approximately 2.5 ns, for high charge hits.
Supervisor: Wascko, Morgan ; Nash, Jordan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral