The semileptonic decays of the B c meson

We study the semileptonic transitions Bc → ηc, J/ψ, D, D∗, B, B∗, Bs, B∗ s in the framework of a relativistic constituent quark model. We use experimental data on leptonic J/ψ decay, lattice and QCD sum rule results on leptonic Bc decay, and on radiative ηc transitions to adjust the quark model parameters. We compute all form factors of the above semileptonic Bc-transitions and give predictions for various semileptonic Bc decay modes including their τ modes when they are kinematically accessible. The implications of heavy quark symmetry for the semileptonic decays are discussed and are shown to be manifest in our explicit relativistic quark model calculation. A comparison of our results with the results of other calculations is performed.