Predicting the T2K Neutrino Flux and Measuring Oscillation Parameters

This thesis reports the calculation of neutrino production for the T2K experiment; themost precise a priori estimate of neutrino production that has been achieved for anyaccelerator-based neutrino oscillation experiment to date. The production of intenseneutrino beams at accelerator facilities requires exceptional understanding of chainsof particle interactions initiated within extended targets. In this thesis, the calculationof neutrino production for T2K has been improved by using measurements of particleproduction from a T2K replica target, taken by the NA61/SHINE experiment. Thisenabled the reduction of the neutrino production uncertainty to the level of 5%, whichwill have a significant impact on neutrino oscillation and interaction measurements byT2K in the coming years. In addition to presenting the revised flux calculationmethodology in an accessible format, this thesis also reports a joint T2K measurementofmuon neutrino and antineutrino disappearance, and the accompanying electronneutrino and antineutrino appearance, with the updated beam constraint.