Measurement of reactor antineutrino oscillation at SNO+

Abstract: 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 $\Delta m^2_{21}$ = ($7.96^{+0.48}_{-0.42}$) $\times$ 10$^{-5}$ eV$^2$. Constraining $\Delta m^2_{21}$ and $\sin^2\theta_{12}$ with measurements from long-baseline reactor antineutrino and solar neutrino experiments yields $\Delta m^2_{21}$ = ($7.58^{+0.18}_{-0.17}$) $\times$ 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 $73^{+47}_{-43}$ TNU at SNO+.