Search for $J/ψ\rightarrow K^{0}_{S}K^{0}_{S}$ and $ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}$
Using data samples of $(10087\pm 44)\times10^{6}$ $J/ψ$ events and $(2712.4\pm 14.3)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we search for the CP violating decays $J/ψ\rightarrow K^{0}_{S}K^{0}_{S}$ and $ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}$. No significant signals are observed over the expected background yields. The upper limits on their branching fractions are set as $\mathcal{B}(J/ψ\rightarrow K^{0}_{S}K^{0}_{S}) <4.7\times 10^{-9}$ and $\mathcal{B}(ψ(3686)\rightarrow K^{0}_{S}K^{0}_{S}) <1.1\times 10^{-8}$ at the 90% confidence level. These results improve the previous limits by a factor of three for $J/ψ\rightarrow K^{0}_{S} K^{0}_{S}$ and two orders of magnitude for $ψ(3686)\rightarrow K^{0}_{S} K^{0}_{S}$.