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

M. Ablikim, J. Z. Bai

Using 14.0 million $\psi (2S)eventscollectedwiththeBES-IIdetector,asearchforthedecayofthe$\jpsi$toaninvisiblefinalstatein$\psipto$isperformed.The$\jpsi$ peak i…