Measuring Solar Neutrinos in the SNO+ Detector

The SNO+ experiment is a large multi-purpose neutrino detector, currently filled with liquid scintillator. For the first time in a single experiment, SNO+ is able to measure the neutrino oscillation parameters θ₁₂ and Δ m²₂₁ simultaneously through both reactor anti-neutrinos and ⁸B solar neutrinos. The latter approach is demonstrated here, with an analysis of an initial 80 days of scintillator phase data. A Bayesian statistical approach via Markov Chain Monte Carlo is used, allowing for the simultaneous fitting of the oscillation parameters, ⁸B neutrino flux, background components with constraints, and systematic uncertainties. The neutrino oscillation parameter θ₁₂ was measured to be 38.9^∘+8.0∘_-7.9∘, assuming the current global fit flux of ⁸B solar neutrinos. This is consistent with the current global fit result for θ₁₂. A sensitivity study shows that this measurement is statistics-limited, and precision could be improved by a factor of two with two years of livetime, assuming the same backgrounds and selections.