Result Highlights

SNO+ Water phase: 8B solar neutrino flux measurement
Water_solar_cosTheta_6MeV.jpg

In December 2018 we published a measurement of the 8B solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector's deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is 0.25+0.09−0.07 events/kt-day, significantly lower than the measured solar neutrino event rate in that energy range, which is 1.03+0.13−0.12events/kt-day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of 2.53+0.31−0.28(stat.)+0.13−0.10(syst.)×106 cm−2s−1, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments.

 

 

SNO+ Water phase: Invisible nucleon decay search

Nucleon_decay_energyspectrumfull_neutron.jpgIn December 2018 we reported results of a search for nucleon decay through 'invisible' modes, where no visible energy is directly deposited during the decay itself, during the initial water phase of SNO+. However, such decays within the oxygen nucleus would produce an excited daughter that would subsequently de-excite, often emitting detectable gamma rays. A search for such gamma rays yields limits of 2.5×1029 y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and 3.6×1029 y for the partial lifetime of the proton, the latter a 70% improvement on the previous limit from SNO. We also present partial lifetime limits for invisible dinucleon modes of 1.3×1028 y for nn, 2.6×1028 y for pn and 4.7×1028 y for pp, an improvement over existing limits by close to three orders of magnitude for the latter two.