Search for Proton Decay throughp→ν¯K+in a Large Water Cherenkov Detector

We present results of a search for proton decays, $p\to \overline{\nu }{K}^{+}$, using data from a $33\mathrm{kt}̇\mathrm{yr}$ exposure of the Super-Kamiokande detector. Two decay modes of the kaon, $K^{+}\to {\mu }^{+}{\nu }_{\mu }$ and $K^{+}\to {\pi }^{+}{\pi }^0$, were studied. The data were consistent with the background expected from atmospheric neutrinos; therefore a lower limit on the partial lifetime of the proton $\tau /B(p\to \overline{\nu }{K}^{+})$ was found to be $6.7\times {10}^{32}\mathrm{years}$ at $90\%$ confidence level.