Measuring Solar Neutrinos in the SNO+ Detector

Abstract

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 $\theta_{12}$ and $\Delta m^{2}_{21}$ simultaneously through both reactor anti-neutrinos and $^{8}B$ 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, $^{8}B$ neutrino flux, background components with constraints, and systematic uncertainties. The neutrino oscillation parameter $\theta_{12}$ was measured to be $38.9^{\circ+8.0^{\circ}}_{-7.9^{\circ}}$, assuming the current global fit flux of $^{8}B$ solar neutrinos. This is consistent with the current global fit result for $\theta_{12}$. 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.