Search for K0SK0S in J/ψ and ψ(2S) decays

Abstract The CP violating processes J / ψ → K 0 S K 0 S and ψ (2 S )→ K 0 S K 0 S are searched for using samples of 58 million J / ψ and 14 million ψ (2 S ) events collected with the Beijing spectrometer at the Beijing electron–positron collider. No signal is observed, and upper limits on the decay branching ratios are determined to be B (J/ψ→K 0 S K 0 S ) −6 and B (ψ(2S)→K 0 S K 0 S ) −6 at the 95% confidence level.