A relativistic bound-state equation is applied to formulate the nonspectator (or W-exchange) decay rates of D, Ds, and B mesons, and their leptonic decay constants. The nonspectator decay rates are also calculated here in the Dirac-equation limit. In this limit we show that up to a logarithm the nonspectator rate grows with heavy-quark mass like m6, faster than the spectator rate of m5. Including an analysis of experimental D, D0, and Ds decay rates shows that the enhancement of D0 decays from the nonspectator diagram is about a quarter of the contribution from the spectator diagram. The relativistically calculated weak decay constant fB is in the 260300-MeV range. Predictions are also made for nonspectator B, Bs, and Bc decay rates &2.. AE © 1988 The American Physical Society.

We formulate a relativistic bound-state calculation of the decay of (0-+) mesons into two gluons or two photons. The decays of c, b, and b are calculated and a value of s deduced from the total width of c. The calculated value for c2 is in agreement with experiment. The decays of 2 and 2 are calculated and by comparison with experiment and the bound on 2, restrictions are placed on the X, Y, X, and Y mixing coefficients of Rosner. The comparison with the Schrödinger-equation calculations shows that the inclusion of relativistic propagators spreads out the annihilations so that they do not occur at r=0. This suppresses the 2S and higher-level decays, with the greatest suppression for the lightest quarks. © 1987 The American Physical Society.