; Lue, Cai-Dian] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Shen, Yue-Long] Ocean Univ China, Inst Informat Sci & Engn, Qingdao 266100, Peoples R China
; [Lue, Cai-Dian] Chinese Acad Sci, Kavli Inst Theoret Phys China, Beijing 100190, Peoples R China
In the covariant light-front quark model, we investigate the form factors of B-c decays into D, D-*, D-s, D-s(*), eta(c), J/psi, B, B-*, B-s, and B-s(*) mesons. The form factors in the spacelike region are directly evaluated. To extrapolate the form factors to the physical region, we fit the form factors by adopting a suitable three-parameter form. At the maximally recoiling point, b -> u, d, and s transition form factors are smaller than b -> c and c -> d, s form factors, while the b -> u, d, s, and c form factors at the zero-recoiling point are close to each other. In the fitting procedure, we find that parameters in A(2)(c)(B)B(*) and A(2)(c)(B)B(s)(*) strongly depend on decay constants of B-* and B-s(*) mesons. Fortunately, semileptonic and nonleptonic B-c decays are not sensitive to these two form factors. We also investigate branching fractions, polarizations of the semileptonic B-c decays. B-c ->(eta(c),J/psi)l nu and B-c ->(B-s,B-s(*))l nu decays have much larger branching fractions than B-c ->(D,D-*,B,B-*)l nu. For the three kinds of B-c -> Vl nu decays, longitudinal contributions are comparable with the transverse contributions. These predictions will be tested on the ongoing and forthcoming hadron colliders.