Search for invisible modes of nucleon decay in water with the SNO plus detector

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 x 10(29) y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and 3.6 x 10(29) 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 x 10(28) y for nn, 2.6 x 10(28) y for pn and 4.7 x 10(28) y for pp, an improvement over existing limits by close to 3 orders of magnitude for the latter two.