Search for Proton Decay via p -> e^+ pi^0 and p -> mu^+ pi^0 in a Large Water Cherenkov Detector

TL;DR

This study searched for proton decay into specific modes using large water Cherenkov detectors, finding no evidence but setting new lower limits on proton lifetime for these decay channels.

Contribution

It provides the first combined analysis of proton decay modes p -> e^+ pi^0 and p -> mu^+ pi^0 with extensive detector data, establishing improved lifetime limits.

Findings

No candidate events observed for either decay mode.

Set lower lifetime limits of 8.2×10^{33} and 6.6×10^{33} years.

Background expectation was 0.3 events for each mode.

Abstract

We have searched for proton decays via p -> e^+ pi^0 and p -> mu^+ pi^0 using data from a 91.7 kiloton year exposure of Super-Kamiokande-I and a 49.2 kiloton year 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$\times10^{33}$ and 6.6$\times10^{33}$ years at 90% confidence level for p -> e^+ pi^0 and p -> mu^+ pi^0 modes, respectively.