Searches for isospin-violating transitions $\chi_{c0,2} \rightarrow \pi^{0} \eta_{c}$

TL;DR

This study sets the first upper limits on the branching fractions of isospin-violating transitions $oldsymbol{ ext{chi}_{c0,2} ightarrow ext{pi}^0 ext{eta}_c}$ using a large sample of $oldsymbol{ ext{psi}(3686)}$ events at BESIII.

Contribution

It provides the first experimental upper limits on these rare isospin-violating decay modes of $oldsymbol{ ext{chi}_{c0,2}}$ particles, improving understanding of isospin violation in charmonium decays.

Findings

Upper limit on $B( ext{chi}_{c0} ightarrow ext{pi}^0 ext{eta}_c)$ is $1.6 imes 10^{-3}$.

Upper limit on $B( ext{chi}_{c2} ightarrow ext{pi}^0 ext{eta}_c)$ is $3.2 imes 10^{-3}$.

Measurements performed with $106 imes 10^6$ $ ext{psi}(3686)$ events.

Abstract

We present the first upper-limit measurement of the branching fractions of the isospin-violating transitions $\chi_{c0,2} \rightarrow \pi^{0} \eta_{c}$. The measurements are performed using $106\times 10^{6}$ $\psi(3686)$ events accumulated with the BESIII detector at the BEPCII $e^{+}e^{-}$ collider at a center-of-mass energy corresponding to the $\psi(3686)$ mass. We obtained upper limits on the branching fractions at a 90\% confidence level of $B(\chi_{c0} \rightarrow \pi^{0} \eta_{c}) < 1.6 \times 10^{-3}$ and $B(\chi_{c2} \rightarrow \pi^{0} \eta_{c}) < 3.2 \times 10^{-3}$.