Semileptonic and radiative decays of the Bc meson in the light-front quark model

We investigate the exclusive semileptonic Bc→(D,ηc,B,Bs) ν, ηb→Bcν (=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. We quantify the zero-mode contributions to f-(q2) for various semileptonic Bc decays. 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 the zero-mode operator with the initial and final state wave functions. Our results are then compared to the available experimental data and the results from other theoretical approaches. Since the prediction on the magnetic dipole Bc*→Bc+γ decay turns out to be very sensitive to the mass difference between Bc* and Bc mesons, the decay width Γ (Bc*→Bcγ) may help in determining the mass of Bc* experimentally. Furthermore, we compare the results from the harmonic oscillator potential and the linear potential and identify the decay processes that are sensitive to the choice of confining potential. From the future experimental data on these sensitive processes, one may obtain more realistic information on the potential between the quark and antiquark in the heavy meson system.