Abstract: | 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 de-excite, often emitting detectable gamma rays. A search for such
gamma rays yields limits of $2.5 imes 10^{29}$ y at 90% Bayesian credibility
level (with a prior uniform in rate) for the partial lifetime of the neutron,
and $3.6 imes 10^{29}$ 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 $1.3 imes 10^{28}$ y for
$nn$, $2.6 imes 10^{28}$ y for $pn$ and $4.7 imes 10^{28}$ y for $pp$, an
improvement over existing limits by close to three orders of magnitude for the
latter two. |