Evidence of psi(3770) non-DD-bar Decay to J/psi pi+pi-

Evidence of $\psi(3770)$ decays to a non-${D \bar D}$ final state is observed. A total of $6.8 \pm 3.0$ $\psi(3770) \to J/\psi \pi+\pi-$ events are obtained from a data sample of $8.0 \pm 0.5$ $\rm {pb^{-1}}$ taken at center-of-mass energies around 3.773 GeV using the BES-II detector at the BEPC. The branching fraction is determined to be $BF(\psi(3770) \to J/\psi \pi+\pi-) = (0.59\pm 0.26 \pm 0.16)%$, corresponding to the partial width of $\Gamma(\psi(3770) \to J/\psi \pi+\pi-) = (139\pm 61 \pm 41)$ keV.