This paper reports results from 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 deexcite, 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 3 orders of magnitude for the latter two.
Funding
Optical Calibration Development for SNO+; G0753; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/J001007/1
Sussex EPP Rolling Grant 2009; G0332; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/H000887/2