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Charged-current and neutral-current event fraction determination based on fit vertices, time residuals and PMT hit angles for the Sudbury Neutrino Observatory

University of British Columbia

The Sudbury Neutrino Observatory (SNO) aims to improve our understanding of neutrinos and energy-generating processes in the Sun. The central purpose of SNO is to compare the flux of charged-current (CC) and neutral-current (NC) events caused by solar neutrinos. The target in SNO will be 10⁶ kg of D₂O. One plan for enhancing the detection of NC events is by doping the D₂O with ³⁵Cl. This thesis describes maximum likelihood fitters created for the purpose of fitting CC events and for fitting NC events that result from neutron capture by a ³⁵Cl nucleus. For each fit event, likelihood ratios are extracted from these fitters to aid in determining the fraction of each type of event in a data set of unknown mixture. It is concluded that using both timing and angle information marginally improves the ability to discriminate between CC and NC events, compared with using angle information alone. This is seen in the reduced estimated error for a technique that determines the CC event fraction in a 50/50 mixed set of CC and NC events. For prototype sets with 2000 events each, and a mixed set with 950 of each event type, an event fraction determination based on only angle information produces a fraction estimate of 0.494 ± 0.037. With identically sized data sets, an event fraction determination that includes both timing and hit angle information produces and estimate of 0.493 ± 0.034.

Thesis/Dissertation

application/pdf

2009-02-15

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http://hdl.handle.net/2429/4607

Physics

University of British Columbia

UBCV

DSpace