Search for proton decay through p → ν̄K+ in a large water cherenkov detector

We present results of a search for proton decays, $p \to \bar{\nu} K^+$, using data from a 33 kton$\cdot$year exposure of the Super-Kamiokandedetector. 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 $\tau / B(p \to \bar{\nu} K^+)$ was found to be $6.7 \times 10^{32}$ years at 90% confidence level.