Observation of χc0 → ς+ ς ̄ -η and evidence for χc1,2 → ς+ ς ̄ -η

Using (27.12±0.14)×108 ψ(3686) events collected with the BESIII detector, the decay χc0→ς+ς¯-η is observed for the first time with a signal significance of 7.0σ, and evidence for χc1→ς+ς¯-η and χc2→ς+ς¯-η is found with signal significances of 4.3σ and 4.6σ, respectively. The branching fractions are determined to be B(χc0→ς+ς¯-η)=(1.26±0.20±0.13)×10-4, B(χc1→ς+ς¯-η)=(5.10±1.21±0.67)×10-5, and B(χc2→ς+ς¯-η)=(5.46±1.18±0.50)×10-5, where the first uncertainties are statistical, and the second ones are systematic.