Study of the $\chi_{cJ}\rightarrow\Lambda\bar{\Lambda}\eta^\prime$ decays

TL;DR

This study reports the first observation of certain $oldsymbol{ ext{chi}}_{cJ}$ decays into $oldsymbol{ extLambdaar{ extLambda} exteta'}$ with measured branching fractions, using a large sample of $oldsymbol{ extpsi(3686)}$ events.

Contribution

First observation of $oldsymbol{ extchi}_{c0,2} ightarrow extLambdaar{ extLambda} exteta'}$ decays and evidence for $oldsymbol{ extchi}_{c1}$ decay, with precise branching fraction measurements.

Findings

First observation of $ extchi_{c0,2}$ decays to $ extLambdaar{ extLambda} exteta'$.

Evidence for $ extchi_{c1}$ decay with 3.3$oldsymbol{ extsigma}$ significance.

No significant excited $ extLambda$ states or near-threshold enhancements observed.

Abstract

Using a data sample of $(2.712\pm0.014)\times10^{9}$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII collider, we investigate the decays $\chi_{cJ} \rightarrow \Lambda \bar{\Lambda} \eta^\prime$ for $J=0,~1,~2$ via the radiative transition $\psi(3686) \rightarrow \gamma \chi_{cJ}$. The decays $\chi_{c0,2}\rightarrow\Lambda\bar{\Lambda}\eta^\prime$ are observed for the first time, with statistical significances of 6.7$\,\sigma$ and 6.4$\,\sigma$, respectively. Evidence for the decay $\chi_{c1}\rightarrow\Lambda\bar{\Lambda}\eta^\prime$ is found with a statistical significance of 3.3$\,\sigma$. The corresponding branching fractions are measured to be $\mathscr{B}(\chi_{c0}\rightarrow\Lambda\bar{\Lambda}\eta^\prime)=(7.56\pm1.42\pm0.90)\times10^{-5}$, $\mathscr{B}(\chi_{c1}\rightarrow\Lambda\bar{\Lambda}\eta^\prime)=(1.54\pm0.51\pm0.16)\times10^{-5}$, and $\mathscr{B}(\chi_{c2}\rightarrow\Lambda\bar{\Lambda}\eta^\prime)=(3.03\pm0.61\pm0.29)\times10^{-5}$, where the first uncertainties are statistical and the second systematic. No significant excited $\Lambda$ baryon states or $\Lambda\bar{\Lambda}$ near-threshold enhancements are observed.