Observation of a Threshold Enhancement in the ${π}^{+}{π}^{−}$ Spectrum in $ψ(3686)→{π}^{+}{π}^{−}J/ψ$ Decays

Author(s): M. Ablikim et al. (BESIII Collaboration) Based on the $(2712.4±14.4)×{10}^{6}\text{ }ψ(3686)$ events collected with the BESIII detector, we present a high-precision study of the ${π}^{+}{π}^{−}$ mass spectrum in $ψ(3686)→{π}^{+}{π}^{−}J/ψ$ decays. A clear resonancelike structure is observed near the ${π}^{+}{π}^{−}$ mass threshold for the … [Phys. Rev. Lett. 136, 141902] Published Wed Apr 08, 2026