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

Abstract

Search results for nucleon decays $p\to e^{+}X$, $p\to {\mu }^{+}X$, $n\to \nu \gamma$ (where $X$ is an invisible, massless particle) as well as dinucleon decays $np\to e^{+}\nu$, $np\to {\mu }^{+}\nu$ and $np\to {\tau }^{+}\nu$ 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 ${\tau }_{p\to e^{+}X}>7.9\times 10^{32}$ years, ${\tau }_{p\to {\mu }^{+}X}>4.1\times 10^{32}$ years, ${\tau }_{n\to \nu \gamma }>5.5\times 10^{32}$ years, ${\tau }_{np\to e^{+}\nu }>2.6\times 10^{32}$ years, ${\tau }_{np\to {\mu }^{+}\nu }>2.2\times 10^{32}$ years and ${\tau }_{np\to {\tau }^{+}\nu }>2.9\times 10^{31}$ years at a $90\%$ confidence level are obtained. Some of these searches are novel.

Comments: 6 pages, 1 figure; minor corrections, length shortened, matches published version