Search for Nucleon Decay into Charged Anti-lepton plus Meson in Super-Kamiokande I and II

TL;DR

This study searched for specific nucleon decay modes into charged anti-leptons and mesons using Super-Kamiokande data, finding no evidence but setting new lower limits on nucleon lifetimes across multiple decay channels.

Contribution

First comprehensive search for twelve nucleon decay modes into charged anti-leptons and mesons using Super-Kamiokande I and II data, establishing new lifetime limits.

Findings

No significant nucleon decay signals observed.

Lower lifetime limits range from 3.6×10^31 to 8.2×10^33 years.

Data consistent with atmospheric neutrino background.

Abstract

Searches for a nucleon decay into a charged anti-lepton (e^+ or {\mu}^+) plus a light meson ({\pi}^0, {\pi}^-, {\eta}, {\rho}^0, {\rho}^-, {\omega}) were performed using the Super-Kamiokande I and II data. Twelve nucleon decay modes were searched for. The total exposure is 140.9 kiloton \cdot years, which includes a 91.7 kiloton \cdot year exposure (1489.2 live days) of Super-Kamiokande-I and a 49.2 kiloton \cdot year exposure (798.6 live days) of Super-Kamiokande-II. The number of candidate events in the data was consistent with the atmospheric neutrino background expectation. No significant evidence for a nucleon decay was observed in the data. Thus, lower limits on the nucleon partial lifetime at 90% confidence level were obtained. The limits range from 3.6 \times 10^31 to 8.2 \times 10^33 years, depending on the decay modes.