Speaker
Description
SNO+ is a low background multi-purpose detector 2 km underground in Sudbury, Ontario. It is able to detect electron antineutrinos with energies down to 1.8 MeV via inverse beta decays. With the majority of the incoming electron antineutrino flux at SNO+ originating from three nuclear reactors 240, 350 and 355 km away, the detector is well situated to measure neutrino oscillation. In particular, it can measure the survival probability of these electron antineutrinos, which depends on so-called “long baseline” oscillation parameters, namely the mixing angle $\theta_{12}$ and the mass-squared difference $\Delta m^2_{21}$. Using 1.46 ktonne-years of data from May 2022 to July 2025, $\Delta m^2_{21} = \left(7.93_{-0.24}^{+0.21}\right) \times 10^{-5}$ eV$^2$ was measured, with a precision approaching the previous result from the KamLAND experiment $\left(7.54_{-0.18}^{+0.19}\right) \times 10^{-5}$ eV$^2$, and providing a valuable cross-check to the recent measurement by the JUNO collaboration. In addition, electron antineutrinos produced from radioactive decays inside the Earth were detected. This geoneutrino flux was simultaneously measured to be $49_{-12}^{+13}$ TNU at SNO+. The result was obtained by using a novel classifier to distinguish the positron annihilation engendered by inverse beta decays from their primary background: ($\alpha$, n)-induced proton recoils. This provides the only measurement of the geoneutrino flux in the Americas, and the third location worldwide, adding crucial data to a global calculation of the mantle’s radiogenic heat production.
| Keyword-1 | neutrino |
|---|---|
| Keyword-2 | oscillation |
| Keyword-3 | SNO+ |