Searching for multi-nucleon processes in neutrino interactions by proton identification in the fine-grained detectors for T2K

Abstract

T2K is an accelerator-based neutrino experiment designed to observe neutrino oscillations with a baseline of 295 km across Japan from Tokai to Kamioka. Its main goal is to measure oscillation parameters (θ₂₃, Δm²₃₂ and θ₁₃) through νμ (overline{νμ}) disappearance and νe (overline{νe}) appearance channels. It has also begun to provide measurements of CP violation in the neutrino sector combining all four neutrino oscillation channels. However, the precision required for these experiments has resulted in the need to reduce challenging systematic uncertainties. Among all the uncertainties, the largest contribution comes from the neutrino interaction model, where nuclear effects are poorly understood. As neutrinos typically interact on nucleons that are almost always contained within nuclei, one immediately has to confront nuclear effects. Nuclear effects alter the kinematics of out-going particles from neutrino scatterings, and hence affect the neutrino oscillation measurements. Therefore it is crucial to understand the nuclear effects in these neutrino interactions. This dissertation describes the measurement of neutrino-nucleus interactions with no final state pion and at least one final state proton. Differential cross sections are measured as a function of kinematic variables, which utilize both muon and protons. An iterative unfolding technique is used to extract the cross sections. By providing unfolded and efficiency corrected results, this measurement can be more readily compared to theoretical models to allow a better understanding of nuclear effects in neutrino interactions, thereby providing valuable constraints on the systematic uncertainties associated with neutrino oscillation measurements for both T2K and other accelerator-based neutrino experiments.Science, Faculty ofPhysics and Astronomy, Department ofGraduat