Observation of ψ (3686) → Λ Λ ¯ η′ decay

Using a sample of (27.12±0.14)×108 ψ(3686) events collected with the BESIII detector, the decay ψ(3686)→ΛΛ¯η′ with η′ subsequently decaying into γπ+π- and ηπ+π- is observed for the first time. The branching fraction of ψ(3686)→ΛΛ¯η′ is measured to be (7.34±0.94(stat)±0.43(sys))×10-6. No resonant structures are evident in the Λη′, Λ¯η′ and ΛΛ¯ mass spectra.