First observation of J/\psi and \psi(2S) decaying to n K^0_S\bar\Lambda +c.c

TL;DR

This paper reports the first observation and measurement of specific decay modes of J/psi and psi(2S) particles, testing the perturbative QCD 12% rule with a large dataset collected at BESII.

Contribution

It presents the first observation and measurement of J/psi and psi(2S) decays to n K_S^0 ar{\Lambda} + c.c., and tests the perturbative QCD 12% rule with new experimental data.

Findings

First observation of the decay modes.

No enhancement near nar{\Lambda} threshold observed.

Upper limit set on certain decay branching ratio.

Abstract

The decays of $\jpsi$ and $\psip$ to ${n}{K^0_S}\bar{\Lambda}+c.c.$ are observed and measured for the first time, and the perturbative QCD ``12%'' rule is tested, based on $5.8 \times 10^7$ $\jpsi$ and $1.4 \times 10^7$ $\psip$ events collected with BESII detector at the Beijing Electron-Positron Collider. No obvious enhancement near $n\bar{\Lambda}$ threshold in $\jpsi \to {n}{K^0_S}\bar{\Lambda}+c.c.$ is observed, and the upper limit on the branching ratio of $\jpsi \to {K^0_S} X, X \to n \bar \Lambda$ is determined.