Semileptonic B_c decays in the light-front quark model

We investigate the exclusive semileptonic B_c→(D,η_c,B,B_s)ℓνℓ, ηb→B_cℓνℓ(ℓ=e,μ,τ) decays using the light-front quark model constrained by the variational principle for the QCD motivated effective Hamiltonian. The form factors f⁺(q²) and f-(q²) are obtained from the analytic continuation method in the q+=0 frame. While the form factor f⁺(q²) is free from the zero mode, the form factor f-(q²) is not free from the zero mode in the q⁺=0 frame. Using our effective method to relate the non-wave function vertex to the light-front valence wave function, we incorporate the zero-mode contribution as a convolution of zero-mode operator with the initial and final state wave functions.