2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/204486Using 14.0 million $ψ(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 $π^+π^-$ is used to tag $ψ$ 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 $\frac{{\cal B}(\jpsi\ar {invisible})}{{\cal B}(\jpsi\arμ^+μ^-)}$. This is the first search for $J/ψ$ decay to an invisible final state.5 pages, 3 figuresHigh Energy Physics - Experimenttext