Using data samples of (10087±44)×106 J/ψ events and (2712.4±14.3)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, we search for the CP violating decays J/ψ→KS0KS0 and ψ(3686)→KS0KS0. No significant signals are observed over the expected background yields. The upper limits on their branching fractions are set as B(J/ψ→KS0KS0)4.7×10−9 and B(ψ(3686)→KS0KS0)1.1×10−8 at the 90% confidence level. These results improve the previous limits by a factor of three for J/ψ→KS0KS0 and two orders of magnitude for ψ(3686)→KS0KS0.
Ablikim et al. (Thu,) studied this question.