APPLICABILITY OF PERTURBATIVE QCD TO B-]D DECAYS

We examine the applicability of perturbative QCD to B meson decays int o D mesons. We find that the perturbative QCD formalism, which include s Sudakov effects at intermediate energy scales, is applicable to the semileptonic decay B --> Dl nu, when the D meson recoils fast. Followi ng this conclusion, we analyze the two-body nonleptonic decays B --> D pi and B --> DDs. By comparing our predictions with experimental data , we extract the matrix element \V-cb\ = 0.044.