Using a data sample of $4.48\times {10}^8$ $\psi (3686)$ events collected with the BESIII detector, we present a first observation of $\psi (3686)\to p\overline{p}\varphi$, and we measure its branching fraction to be $[6.06\pm 0.38(\mathrm{stat})\pm 0.48(\mathrm{syst})]\times {10}^{-6}$. In contrast to the earlier discovery of a threshold enhancement in the $p\overline{p}$-mass spectrum of the channel $J/\psi \to \gamma p\overline{p}$, denoted as $X(p\overline{p})$, we do not find a similar enhancement in $\psi (3686)\to p\overline{p}\varphi$. An upper limit of $1.82\times {10}^{-7}$ at the 90% confidence level on the branching fraction of $\psi (3686)\to X(p\overline{p})\varphi \to p\overline{p}\varphi$ is obtained.

• Received 26 February 2019

DOI:https://doi.org/10.1103/PhysRevD.99.112010

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Published by the American Physical Society