Measurement of |V_ub/V_cb| (and |V_ub|) in exclusive nonleptonic decays within the generalized factorization scheme

Within the generalized factorization scheme, we study extracting |V_ub/V_cb| by calculating the ratios B(B° →D_s^-(π⁺,ρ ⁺))/(B°-tD^-D⁺) including penguin effects. The ratios involving the B°→D^-D⁺ mode have considerable penguin corrections (-15% at the amplitude level), but those involving the B° →D_sD⁺ mode have relatively small penguin corrections. On the other hand, the B°→D^-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_cj| from the exclusive semileptonic B decays. Using the newest upper limit on B->DSπ 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.