A Study of Neutrino Oscillation Models with Super-Kamiokande Atmospheric Neutrino Data

Abstract

The rapidly evolving field of neutrino oscillations continues to offer exciting experimental results as it enters the era of precision measurements. The mixing angles and mass-squared splittings governing neutrino oscillations have all been measured experimentally and only one parameter, the CP-violating phase δ, remains unmeasured. Both atmospheric and long-baseline accelerator experiments are sensitive to the parameters θ₂₃ and Δm<super>2</super>_{23}. In particular the wide range of neutrino pathlengths and energies accessible to the Super-Kamiokande (SK) detector with atmospheric neutrinos offer a unique opportunity to measure these parameters with high-statistics data. SK is also suitable for constraining exotic oscillation models which include sterile neutrinos and non-standard matter interactions, due to the large variations in density through which atmospheric neutrinos can traverse. In this thesis we use an expanded atmospheric neutrino dataset combined with improved Monte Carlo simulations to update the SK 2-flavor muon neutrino disappearance zenith angle analysis. We measure values of Δm<super>2</super>₂₃ = 2.30<super>+0.17</super>_-0.22 x 10<super>-3</super> eV<super>2</super> and sin<super>2</super> 2θ₂₃ > 0.95 (90% C.L.), in excellent agreement with recent worldwide results. We also fit the SK data to a recent exotic model which incorporates both sterile-active mixing and a new non-standard interaction in matter. We find that SK rules out most of the model's parameter space and restricts it to the region where standard 2-flavor mixing is recovered.