Combined Study of Reactor and Terrestrial Antineutrinos with KamLAND

This dissertation presents a combined study of antineutrinos of terrestrial and reactor origin detected by Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND). Of special physical interest are neutrino oscillation parameters and the terrestrial antineutrino flux, the former being of a profound importance for new physics beyond the Standard Model, and the latter having significant implications for geophysics. The analysis described here uses a comprehensive likelihood model to naturally combine terrestrial and reactor antineutrino studies within a single framework. The use of this likelihood model and better event reconstruction tools allowed to obtain narrower limits for the oscillation parameters and the terrestrial antineutrino fluxes than separate reactor and terrestrial antineutrino KamLAND studies had provided before.

Based on 944.4 days of exposure, neutrino oscillation parameters ∆m² ₁₂, sin² 2θ₁₂ are obtained to be 7.52^+0.19 _-18× 10−5 eV ² and 0.916^+0.084 _-0.134, respectively, at 0.68 confidence level (CL).

The terrestrial antineutrino rate at KamLAND site is determined to be 46.6^+19.9 _-19.2 TNU (Terrestrial Neutrino Units, i.e. events per 10³² protons per year) at 0.68 CL.