CCAST, World Lab, Beijing 100080, Peoples R China
; Inst High Energy Phys, Beijing 100049, Peoples R China
The ratio of KSKS (KLKL) and KSKL production rates is calculated by considering K-0-(K) over bar (0) oscillation in J/psi -> K-0(K) over bar (0) decay. The theoretical uncertainty due to strong interaction in J/psi decay is completely canceled in the ratio; therefore, the absolute branching fractions of the CP-violating processes of J/psi -> KSKS and KLKL can be cleanly and model-independently determined in the case that J/psi -> KSKL decay is precisely measured. In the future tau-charm factory, the expected CP violating process of J/psi -> KSKS should be reached. It is important to measure J/psi to KSKS and KSKL decays simultaneously, so that many systematic errors will be canceled. More precise measurements are suggested to examine the predicted isospin relation in J/psi -> K (K) over bar decays. All results can be extended to decays of other vector quarkonia, phi, psi(2S), and Upsilon(1S), etc.