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Title: Reconstruction of neutrino induced neutral current neutral pion events with the T2K ND280 Tracker and ECAL
Author: Guzowski, Pawel
ISNI:       0000 0004 2736 9182
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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T2K is a long baseline neutrino oscillation experiment in Japan. One of the goals is to search for electron neutrino appearance at the far detector (Super Kamiokande) in a muon neutrino beam produced 295 km away, to make a measurement of the unknown neutrino oscillation angle [Symbol appears here. To view, please open pdf attachment]13. A major background to this appearance search is neutral pions (π0) produced in neutral current (NC) neutrino interactions. The π0s decay to photons, which can in cases mimic the electron appearance signal. The near detector of the experiment (ND280) has the capability of measuring the rates of NCπ0 production processes. NCπ0 interactions in the Tracker of the detector (plastic scintillator targets, and time projection chambers for tracking charged particles) can be detected through photon conversions in the electromagnetic calorimeter that surrounds the Tracker. For these types of events, the photon reconstruction in the calorimeter has to have good energy and angular resolutions. This thesis describes the T2K experiment, the ND280 detector and its offline software, and gives details on the ECal reconstruction of photons. The performance of the reconstruction in relation to the π0 decay photons, their energy and angular resolutions, is studied. An analysis is presented for the reconstruction of NC π0s produced in the trackers, with both photons converting in the downstream calorimeter, developed purely with Monte Carlo (with GENIE as the interaction generator), and then applied to the first-year data from ND280. The Monte Carlo expectation is 17.7 ± 1.1(stat) ± 4.9(syst) events, with 37 ± 4% NCπ0 purity; 21 events are seen in the first year data. The MC is consistent with data at the 0.5σ level. As a crosscheck, the same analysis is applied to a different Monte Carlo production (using NEUT as the generator). The expectation from this production is 16.8 ± 1.0(stat) ± 4.7(syst) events, with 30 ± 4% purity. This is consistent with data at the 0.7σ level.
Supervisor: Wascko, Morgan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral