Vector-to-vector-plus-pseudoscalar decay modes in perturbative QCD.

Abstract

We calculate branching ratios for the Okubo-Zweig-Iizuka-rule-suppressed decays of a flavorneutral vector meson ($\ensuremath{\Upsilon},\frac{J}{\ensuremath{\psi}}$) into a vector meson plus a pseudoscalar meson, in perturbative QCD. The final mesons may be flavored or flavor neutral. The initial and final mesons are assumed to be nonrelativistic quark-antiquark bound states. The calculation is made to lowest order in strong coupling, and in the average relative momentum of the constituent quarks of each of the mesons. The only input parameters for our calculations are the strong coupling and the bound-state wave functions at the origin, which (for flavor-neutral mesons) are all determined from known hadronic and leptonic widths. Our calculations can therefore provide parameter-free tests of QCD, when applied to $\ensuremath{\Upsilon}$-to-charmonium transitions, where the approximations are most reliable. Results for decays of the $\frac{J}{\ensuremath{\psi}}$ are in reasonable accord with the experimental data, taking into account the roughness of the approximations for the light final-state mesons.