Search for the Invisible Decay of $\jpsi$ in $\psi(2S)\to\pi+\pi^-J/\psi$

Abstract

Using 14.0 million $\psi(2S) events collected with the BES-II detector, a search for the decay of the $\jpsi$ to an invisible final state in $\psipto$ is performed. The $\jpsi$ peak in the distribution of mass recoiling against the $\pi^+\pi^-$ is used to tag $\psi$ invisible decay. No signal is found, and an upper limit at the 90% confidence level is determined to be $1.2\times 10^{-2}$ for the ratio $\frac{{\cal B}(\jpsi\ar {invisible})}{{\cal B}(\jpsi\ar\mu^+\mu^-)}$. This is the first search for $J/\psi$ decay to an invisible final state.