Measurement of the Branching Fraction for the Decay $ψ(3686) \rightarrow ϕK_{S}^{0} K_{S}^{0}$

Based on $(448.1 \pm 2.9 )\times 10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decay $ψ(3686)\rightarrow ϕK_{S}^{0} K_{S}^{0}$ is observed for the first time. Taking the interference between $ψ(3686)$ decay and continuum production into account, the branching fraction of this decay is measured to be $\mathcal{B}(ψ(3686)\rightarrowϕK_S^0 K_S^0 )$ = $(3.53 $ $\pm$ $0.20$ $\pm$ $0.21$)$\times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. Combining with the world average value for ${\mathcal B}(J/ψ\to ϕK^0_SK^0_S)$, the ratio $\mathcal{B}(ψ(3686)\rightarrow ϕK_{S}^{0} K_{S}^{0})/\mathcal{B}(J/ψ\rightarrow ϕK_{S}^{0} K_{S}^{0}) $ is determined to be $(6.0\pm 1.6)$%, which is suppressed relative to the 12% rule.