Our understanding of the physics of neutrino oscillations
has evolved rapidly over the past decade or so, with results from the SNO,
Super-K, MINOS and CHOOZ experiments, among others, producing results favouring
a three-neutrino mixing model, and significantly constraining the parameter
space for the mixing.
There are still several important questions to be answered
however: we do not know whether theta_13 is non-zero, or whether (sin^2 (2*theta_23))
is maximal; also, we do not know the sign of the mass splitting Delta M^2, or
whether CP-violation occurs in the lepton sector. The latter is possibly the
most exciting of all - leptonic CP-violation is a requirement for leptogenesis,
and could therefore indicate a solution to the matter-antimatter asymmetry
problem in cosmology. The T2K long-baseline neutrino experiment is one of a new
generation of neutrino projects, which will make more precise measurements of
theta_13 and theta_23 than has been achieved by previous experiments. It uses
the Super-K water Cerenkov detector at Kamioka as a far detector, and also has
a suite of new near detectors.
These are largely scintillator-based, but use a novel
photosensor, the silicon photomultiplier (SiPM), for light readout. T2K has
been leading the effort understand and model these new sensors, and the present
work will describe the current state-of-the-art in device characterisation, and
also the effort to ensure the quality of the devices installed in the
calorimeter of the ND280 near detector. An important part of a long-baseline
analysis is the extrapolation of the neutrino flux measured at the near
detector to predict that at the far detector. Methods to do this have been
developed by previous experiments; however T2K uses an innovative configuration
whereby the main detectors are displaced from the neutrino beam centre,
removing much of the high-energy tail in the neutrino flux to reduce
backgrounds from non-quasielastic events. This thesis evaluates the
effectiveness of two extrapolation techniques, used by previous experiments,
for the T2K configuration.
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