Flavor changing processes in quarkonium decays

We study the flavor changing processes Υ-->B/B¯X_s and J/ψ-->D/D¯X_u in B factories and tau-charm factories. In the standard model, these processes are predicted to be unobservable; so they serve as a probe of new physics. We first perform a model-independent analysis, then examine the predictions of the models, such as the top-color models, the MSSM with R-parity violation, and the two-Higgs-doublet model, for the branching ratios of Υ-->B/B¯X_s and J/ψ-->D/D¯X_u. We find that these branching ratios could be as large as 10^-6 and 10^-5 in the presence of new physics.