Measurement of \|Vub/Vcb\| (and \|Vub\|) in exclusive nonleptonic decays within the generalized factorization scheme
Within the generalized factorization scheme, we study extracting \|Vub/Vcb\| by calculating the ratios B(B¯0-->D(*)- s(pi+,rho+))/B(B¯0-->D(*)-sD(*)+) including penguin effects. The ratios involving the B¯0-->D-sD+ mode have considerable penguin corrections (~15% at the amplitude level), but those involving the B¯0-->D-sD*+ mode have relatively small penguin corrections. On the other hand, the B¯0-->D-sD+ mode has a smaller form-factor dependence. Therefore, these ratios complement each other in measuring Vub/Vcb. 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 \|Vub/Vcb\| from the exclusive semileptonic B decays. Using the newest upper limit on B-->Dspi decay from CLEO, our method sets an upper limit \|Vub/Vcb\|<0.13 which is very close to the measured values from the semileptonic B decays.