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

The CP violating processes J/ψ→K0SK0S and ψ(2S)→K0SK0S are searched for using samples of 58 million J/ψ and 14 million ψ(2S) 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→K0SK0S)<1.0×10−6 and B(ψ(2S)→K0SK0S)<4.6×10−6 at the 95% confidence level.