Observation of

Based on (2712 4 ± 14 3) × 10 (3686) events collected at the BESIII detector operating at the BEPCII collider, we present the first observation of the decay + c.c.. The product branching fraction is measured to be (9 47 ± 0 75 ± 0 97) × 10 7 , where the first uncertainty is statistical and the second systematic.