Abstract: | Search results for nucleon decays $p
ightarrow e^+X$, $p
ightarrow
mu^+X$, $n
ightarrow
ugamma$ (where $X$ is an invisible, massless
particle) as well as di-nucleon decays $np
ightarrow e^+
u$, $np
ightarrow
mu^+
u$ and $np
ightarrow au^+
u$ 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 $ au_{p
ightarrow
e^+X} > 7.9 imes 10^{32}$ years, $ au_{p
ightarrow mu^+X} > 4.1 imes
10^{32}$ years, $ au_{n
ightarrow
ugamma} > 5.5 imes 10^{32}$ years,
$ au_{np
ightarrow e^+
u} > 2.6 imes 10^{32}$ years, $ au_{np
ightarrow mu^+
u} > 2.2 imes 10^{32}$ years and $ au_{np
ightarrow
au^+
u} > 2.9 imes 10^{31}$ years at a $90 \% $ confidence level are
obtained. Some of these searches are novel. |