First observation of J/ψand ψ(2S) decaying to n K^0_S\barΛ+c.c

Abstract

The decays of $\jpsi$ and $\psip$ to $n{K}_S^0\bar{\hat{I}}›+c.c.$ 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 $n\bar{\hat{I}}›$ threshold in $\jpsi \to {n}{K^0_S}\barΛ+c.c.$ is observed, and the upper limit on the branching ratio of $\jpsi \to {K^0_S} X, X \to n \bar Λ$ is determined.

10 pages, 10 figures