Measurement of |Vub/Vcb| (and |Vub|) in exclusive nonleptonic decays within the generalized factorization scheme -: art. no. 094506

Within the generalized factorization scheme, we study extracting \V-ub/V-cb\ by calculating the ratios B((B) over bar (0) -->D-s((*)-)(pi (+),rho (-)))/B((B) over bar (0)-->Ds(*)-D(*)+) including penguin effects. The ratios involving the (B) over bar (0)-->Ds-D+ mode have considerable penguin corrections (similar to 15% at the amplitude level), but those involving the (B) over bar (0) -->Ds-D*(+) mode have relatively small penguin corrections. On the Other hand, the (B) over bar (0)-->Ds-D+ mode has a smaller form-factor dependence. Therefore, these ratios complement each other in measuring V-ub/V-cb. The theoretical uncertainty from the hadronic form factors in our method is at the level of 20%, which is comparable to the model dependence uncertainty of about 20% in the measurement of \V-ub/V-cb\ from the exclusive semileptonic B decays. Using the newest upper limit on B-->D(s)pi decay from CLEO, our method sets an upper limit \V-ub/V-cb\ < 0.13 which is very close to the measured values from the semileptonic B decays.