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

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 $\hat{I}”m_{21}^2=(7.93_{-0.24}^{+0.21})\times 10^{-5}$ 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: $\hat{I}”m_{21}^2$ = $(7.63\pm 0.17)\times 10^{-5}$ eV${}^2$ and ${\sin }^2\hat{I}{¸}_{12}=0.310\pm 0.012$. The analysis of geoneutrinos at SNO+ is also improved, with a measured signal of 49${}_{-12}^{+13}$ TNU.