Search for Nucleon and Dinucleon Decays with an Invisible Particle and a Charged Lepton in the Final State at the Super-Kamiokande Experiment

Search results for nucleon decays $p\to e^{+}X$, $p \rightarrow \mu^+X$,$n \rightarrow \nu\gamma$(where$X$ is an invisible, massless particle) as well as dinucleon decays $np\to e^{+}\nu$, $np \rightarrow \mu^+\nu$and$np \rightarrow \tau^+\nu$ in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton $\cdot$ years, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of $\tau_{p \rightarrow e^+X} > 7.9 \times 10^{32}$years,$\tau_{p \rightarrow \mu^+X} > 4.1 \times 10^{32}$years,$\tau_{n \rightarrow \nu\gamma} > 5.5 \times 10^{32}$years,$\tau_{np \rightarrow e^+\nu} > 2.6 \times 10^{32}$years,$\tau_{np \rightarrow \mu^+\nu} > 2.2 \times 10^{32}$yearsand$\tau_{np \rightarrow \tau^+\nu} > 2.9 \times 10^{31}$yearsata$90 % $ confidence level are obtained. Some of these searches are novel.