Measurement of reactor antineutrino oscillation at SNO+

The SNO+ collaboration reports its second spectral analysis of reactor antineutrino oscillation using 286 tonne-years of new data. The measured energies of reactor antineutrino candidates were fitted to obtain the second-most precise determination of the neutrino mass-squared difference $\mathrm{\Delta }{m}_{21}^2$ = ($7.96_{-0.42}^{+0.48}$) $\times$ 10${}^{-5}$ eV${}^2$. Constraining $\mathrm{\Delta }{m}_{21}^2$ and ${\sin }^2{\theta }_{12}$ with measurements from long-baseline reactor antineutrino and solar neutrino experiments yields $\mathrm{\Delta }{m}_{21}^2$ = ($7.58_{-0.17}^{+0.18}$) $\times$ 10${}^{-5}$ eV${}^2$ and ${\sin }^2{\theta }_{12}=0.308\pm 0.013$. This fit also yields a first measurement of the flux of geoneutrinos in the Western Hemisphere, with $73_{-43}^{+47}$ TNU at SNO+.