Reactor Antineutrino Oscillations and Geoneutrinos in SNO+

TL;DR

SNO+ uses reactor and geoneutrino data to precisely measure neutrino oscillation parameters and the Earth's geoneutrino flux, confirming consistency with existing models and measurements.

Contribution

First measurement of geoneutrino flux in the Western Hemisphere and precise determination of m in a multipurpose liquid-scintillator detector.

Findings

Measured m = (7.93^{+0.21}_{-0.24}) imes 10^{-5} eV^2, consistent with other experiments.

First geoneutrino flux measurement in the Western Hemisphere: 49^{+13}_{-12} TNU.

Spectral analysis simultaneously fitting oscillation parameters, flux, background, and systematics.

Abstract

SNO+ is a multipurpose liquid-scintillator neutrino detector located 2 km underground at SNOLAB, Canada. Three large nuclear reactors at baselines of 240-350 km allow a precise measurement of the neutrino oscillation parameter $\Delta m^2_{21}$ and, to a lesser extent, $\theta_{12}$. A spectral analysis is performed, simultaneously fitting $\Delta m^2_{21}$, $\theta_{12}$, the reactor antineutrino flux, background rates, and associated systematics. Using data collected between May 2022 and July 2025, corresponding to a livetime of 685 days, a value of $\Delta m^2_{21} = (7.93^{+0.21}_{-0.24}) \times 10^{-5}$ eV$^2$ is obtained. This result is compatible with other long-baseline reactor antineutrino measurements by KamLAND and JUNO. SNO+ has also made the first measurement of the geoneutrino flux in the Western Hemisphere, measuring $49^{+13}_{-12}$ TNU, in agreement with predictions from geological models.