Search for nucleon decay into charged antilepton plus meson in 0.316 megaton$\cdot$years exposure of the Super-Kamiokande water Cherenkov detector

Abstract

We have searched for proton decays into a charged antilepton ($e^+$, $\mu^+$) plus a meson ($\eta$, $\rho^0$, $\omega$) and neutron decays into a charged antilepton ($e^+$, $\mu^+$) plus a meson ($\pi^-$, $\rho^-$) using Super-Kamiokande (SK) I-IV data, corresponding to 0.316 megaton$\cdot$years of exposure. This measurement updates the previous published result by using 2.26 times more data and improved analysis methods. No significant evidence for nucleon decay has been observed and lower limits on the partial lifetime of the nucleon are obtained. The limits range from 3$\times$10$^{31}$ to 1$\times$10$^{34}$ years at 90% confidence level, depending on the decay mode.