Decays of B meson to two charmed mesons

The factorization theorem in decays of B_(s) mesons to two charmed mesons (both pseudoscalar and vector) can be proved in the leading order in m_D/m_B and Λ_QCD/m_D expansion. Working in the perturbative QCD approach, we find that the factorizable emission diagrams are dominant. Most of branching ratios we compute agree with the experimental data well, which means that the factorization theorem seems to be reliable in predicting branching ratios for these decays. In the decays of a B meson to two vector charmed mesons, the transverse polarization states contribute 40%-50% both in the processes with an external W emission and in the pure annihilation decays. This is in agreement with the present experimental data. We also calculate the CP asymmetry parameters. The results show that the direct CP asymmetries are very small. Thus observation of any large direct CP asymmetry will be a signal for new physics. The mixing induced CP asymmetry in the neutral modes is large. This is also in agreement with the current experimental measurements. They can give a cross-check of the sin⁡2β measurement from other channels.