Measurement of reactor antineutrino oscillations with 1.46 ktonne-years of data at SNO+

TL;DR

This paper presents new measurements of reactor antineutrino oscillations and geoneutrino signals at SNO+ using 1.46 ktonne-years of data, refining neutrino oscillation parameters and improving geoneutrino detection.

Contribution

First measurement of reactor antineutrino oscillation parameters at SNO+ with high precision, and improved geoneutrino flux analysis.

Findings

Measured $ ext{Δ}m^2_{21}=(7.93^{+0.21}_{-0.24})\times 10^{-5}$ eV$^2$

Combined data yields $ ext{Δ}m^2_{21}=(7.63\pm0.17)\times 10^{-5}$ eV$^2$ and $ ext{sin}^2\theta_{12}=0.310\pm0.012$

Geoneutrino signal measured as 49$^{+13}_{-12}$ TNU

Abstract

The SNO+ Collaboration reports new results on reactor antineutrino oscillations using data acquired from May 2022 through July 2025. The spectral analysis of a flux dominated by nuclear reactors at 240, 350, and 355 kilometers yields the mass-squared difference $\Delta m^2_{21}=(7.93^{+0.21}_{-0.24})\times 10^{-5}$ eV$^2$. This result is compatible with and approaches the precision of the only other long-baseline reactor antineutrino measurement, by KamLAND. Combining these measurements, along with those from solar neutrino experiments, the global values of the neutrino mixing parameters become: $\Delta m^2_{21}$ = $(7.63\pm0.17)\times 10^{-5}$ eV$^2$ and $\sin^2{\theta_{12}}=0.310\pm0.012$. The analysis of geoneutrinos at SNO+ is also improved, with a measured signal of 49$^{+13}_{-12}$ TNU.