Observation of ψ (3686) →p p φ OBSERVATION of ψ (3686) →p p φ M. ABLIKIM et al.

Using a data sample of 4.48×108 ψ(3686) events collected with the BESIII detector, we present a first observation of ψ(3686)→pp φ, and we measure its branching fraction to be [6.06±0.38(stat)±0.48(syst)]×10-6. In contrast to the earlier discovery of a threshold enhancement in the pp-mass spectrum of the channel J/ψ→γpp, denoted as X(pp), we do not find a similar enhancement in ψ(3686)→ppφ. An upper limit of 1.82×10-7 at the 90% confidence level on the branching fraction of ψ(3686)→X(pp)φ→ppφ is obtained.