A detailed analysis ofD-,D s - andB-meson transition form factors and the determination of |V cb |

Abstract

We study various transition form factors in semi-leptonic decays ofD-,Ds-,B- andBs-mesons using the pole dominance assumption. The vector current form factor is found to have only a negligible contribution to the decay rates involving pseudoscalar to vector transitions. In view of this fact we evaluate the form factors from present experimental data on the exclusive semi-leptonic decay rateΓ and the ratioΓl/ΓT of the longitudinal and transverse partial decay rates. Some non-leptonic two-body decay rates are also investigated using the factorization ansatz. Consistency with the semi-leptonic decays is found. The transition form factors of theD- andDs-mesons are found to contradict the predictions of quark model. In contrast, the experimental data on the transition form factors ofB-mesons are found to be consistent with the quark model predictions. The KM matrix element |Vcb| is determined to be |Vcb|=0.040±0.010, a value somewhat smaller than is usually chosen.