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 $11.8 \pm 4.8$ $\psi(3770) \to J/\psi \pi^+\pi^-$ events are obtained from a data sample of 27.7 $\rm {pb^{-1}}$ 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 $BF(\psi(3770) \to J/\psi \pi^+\pi^-) =(0.34\pm 0.14 \pm 0.08)%$, corresponding to the partial width of $\Gamma(\psi(3770) \to J/\psi \pi^+\pi^-) = (80 \pm 32 \pm 21)$ keV.