Search for Proton Decay via p→e+π0 and p→μ+π0 in a Large Water Cherenkov Detector

We have searched for proton decays via p→e⁺π⁰ and p→μ⁺π⁰ using data from a 91.7kt·yr exposure of Super-Kamiokande-I and a 49.2kt·yr exposure of Super-Kamiokande-II. No candidate events were observed with expected backgrounds induced by atmospheric neutrinos of 0.3 events for each decay mode. From these results, we set lower limits on the partial lifetime of 8.2×10³³ and 6.6×10³³ years at 90% confidence level for p→e⁺π⁰ and p→μ⁺π⁰ modes, respectively.