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Title: Atmospheric neutrino observations in the MINOS far detector
Author: Chapman, J. D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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This thesis presents the results of atmospheric neutrino observations from a 12.23 ktyr exposure of the 5.42 kt MINOS Far Detector between 1st August 2003 until 1st March 2006. The separation of atmospheric neutrino events from the large background of cosmic muon events is discussed. A total of 277 candidate contained vertex v/μ CC data events are observed, with an expectation of 354.4±47.4 events in the absence of neutrino oscillations. A total of 182 events have clearly identified directions, 77 data events are identified as upward going, 105 data events are identified as downward going. This is 2.1σ away from the expectation for no oscillations. A total of 167 data events have clearly identified charge, 112 are identified as vμ events, 55 are identified as μ events. This is the largest sample of charge-separated contained-vertex atmospheric neutrino interactions so far observed. Bayesian methods were used to generate a log (L/E) PDF for each settled event with a clearly identified direction. This information was used to give a measure of the uncertainty in the reconstructed log(L/E) value for each event. A maximum likelihood analysis is used to determine the allowed regions for the oscillation parameters Δm232 and sin22θ23. The likelihood function uses the uncertainty in log(L/E) to bin events in order to extract as much information from the data as possible. This fit rejects the null oscillations hypothesis at the 98% confidence level. A fit to independent vμ and μ oscillation assuming maximal mixing for both is also performed. The projected sensitivity after an exposure of 25 ktyr is also discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available