Evidence of ψ(3770) non-DD¯ decay to J/ψπ+π−

Evidence of ψ(3770) decays to a non-DD¯ final state is observed. A total of 11.8±4.8±1.3ψ(3770)→J/ψπ+π− events are obtained from a data sample of 27.7 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(ψ(3770)→J/ψπ+π−)=(0.34±0.14±0.09)%, corresponding to the partial width of Γ(ψ(3770)→J/ψπ+π−)=(80±33±23)keV.