Observation of the decay ψ(3686) → ${\Sigma }^{-}{\overline{\Sigma }}^{+}$ and measurement of its angular distribution

Using (448.1 ± 2.9) × 106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, the decay ψ(3686) → ${\Sigma }^{-}{\overline{\Sigma }}^{+}$ is observed for the first time with a branching fraction of (2.82 ± 0.04stat. ± 0.08syst. ) × 10 −4, and the angular parameter α Σ− is measured to be 0.96 ± 0.09stat. ± 0.03syst. .