Search for the isospin-violating decays $\boldsymbol{\chi_{cJ}\to\Lambda\bar{\Sigma}^{0}+c.c.}$ and $\boldsymbol{\eta_{c}\to\Lambda\bar{\Sigma}^{0}+c.c.}$

TL;DR

This study searches for isospin-violating decays of certain charmonium states into Lambda and Sigma baryons, setting the first upper limits on their branching fractions with no significant signals observed.

Contribution

First experimental search for these isospin-violating decays, establishing upper limits on their branching fractions using a large BESIII dataset.

Findings

No significant signals detected for the decays.

Upper limits on branching fractions are set at 90% confidence level.

First constraints on these rare decay modes.

Abstract

Using a sample of $(2712.4\pm14.3)\times10^{6}$~$\psi(3686)$ events collected with the BESIII detector, we perform a search for the isospin-violating decays $\chi_{cJ}\to\Lambda\bar{\Sigma}^{0}+c.c.~(J=0,1,2)$ and $\eta_{c}\to\Lambda\bar{\Sigma}^{0}+c.c.$ No significant signal for $\chi_{cJ}$ or $\eta_{c}$ is observed in the $\Lambda\bar{\Sigma}^{0}$ invariant mass distribution. The upper limits on the branching fractions at the 90\% confidence level are set to be $\mathcal{B}$($\chi_{c0}\to\Lambda\bar{\Sigma}^{0}+c.c.$)$<1.5\times 10^{-6}$, $\mathcal{B}$($\chi_{c1}\to\Lambda\bar{\Sigma}^{0}+c.c.$)$<1.6\times 10^{-6}$, $\mathcal{B}$($\chi_{c2}\to\Lambda\bar{\Sigma}^{0}+c.c.$)$<1.7\times 10^{-6}$ and $\mathcal{B}$($\eta_{c}\to\Lambda\bar{\Sigma}^{0}+c.c.$)$<6.2\times 10^{-5}$ for the first time.