Measurements of the branching fractions of $\psi(3686)\rightarrow\bar{\Sigma}^{0}\Lambda+c.c.$ and $\chi_{cJ (J = 0,1,2)} \rightarrow \Lambda \bar{\Lambda}$

TL;DR

This study measures branching fractions of specific charmonium decays using BESIII data, finding results that refine previous measurements and provide new insights into isospin violation and decay dynamics.

Contribution

First measurement of the isospin violating decay $oldsymbol{ ext{ψ(3686)} ightarrow ar{ ext{Σ}}^{0} ext{Λ} + c.c.}$ and updated branching fractions for $oldsymbol{ ext{χ}_{cJ} ightarrow ext{Λ}ar{ ext{Λ}}}$ decays.

Findings

The branching fraction of $ ext{ψ(3686)} ightarrow ar{ ext{Σ}}^{0} ext{Λ} + c.c.$ is $(1.60 imes 10^{-6})$, smaller than previous CLEO-c results.

Branching fractions for $ ext{χ}_{c0,1,2} ightarrow ext{Λ}ar{ ext{Λ}}$ are measured as approximately $3.64$, $1.31$, and $1.91 imes 10^{-4}$ respectively.

Results improve understanding of charmonium decay mechanisms and isospin violation effects.

Abstract

Based on $4.481\times10^8$ $\psi(3686)$ events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay $\psi(3686)\rightarrow\bar{\Sigma}^{0}\Lambda+c.c.$ is measured to be $(1.60 \pm 0.31 \pm 0.13~\pm~0.58) \times 10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays $\chi_{cJ} \rightarrow\Lambda\bar{\Lambda}$ are measured via $\psi(3686)\rightarrow\gamma\chi_{cJ}$, and the branching fractions are determined to be $\mathcal{B}\left(\chi_{c0}\rightarrow\Lambda\bar{\Lambda}\right)=(3.64 \pm 0.10 \pm 0.10 \pm 0.07)\times 10^{-4}$, $\mathcal{B}\left(\chi_{c1}\rightarrow\Lambda\bar{\Lambda}\right)=(1.31\pm0.06 \pm 0.06 \pm0.03)\times 10^{-4}$, $\mathcal{B}\left(\chi_{c2}\rightarrow\Lambda\bar{\Lambda}\right)=(1.91\pm0.08 \pm 0.17 \pm0.04)\times 10^{-4}$, where the third uncertainties are systematic due to the $\psi(3686) \rightarrow \gamma \chi_{c J}$ branching fractions.