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

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