Search for the hyperon semileptonic decay $\Xi^{-} \rightarrow \Xi^{0} e^{-} \bar{\nu_{e}}$

TL;DR

This paper reports a search for a specific hyperon decay using a large dataset, setting a new upper limit on its branching fraction, which improves previous constraints by an order of magnitude.

Contribution

The study provides the most stringent upper limit to date on the branching fraction of the hyperon decay $\Xi^{-} ightarrow \Xi^{0} e^{-} ar{ u}_{e}$, using BESIII data.

Findings

No significant signal observed.

Upper limit on branching fraction set to 2.59×10⁻⁴.

Result improves previous limit by an order of magnitude.

Abstract

Using $(10.087\pm0.044)\times10^{9}$ $J/\psi$ events collected by the BESIII detector at the BEPCII collider, we search for the hyperon semileptonic decay $\Xi^{-} \rightarrow \Xi^{0} e^{-} \bar{\nu}_{e}$. No significant signal is observed and the upper limit on the branching fraction $\mathcal B(\Xi^{-} \rightarrow \Xi^{0} e^{-} \bar{\nu}_{e})$ is set to be $2.59\times10^{-4}$ at 90 % confidence level. This result is one order of magnitude more strict than the previous best limit.