Light-Front Quark Model Analysis of Exclusive $0^{-} \to 0^{-}$ Semileptonic Heavy Meson Decays

We present the analysis of exclusive $0^{-} \to 0^{-}$ semileptonic heavy meson decays using the constituent quark model based on the light-front quantization. Our model is constrained by the variational principle for the well-known linear plus Coulomb interaction motivated by QCD. Our method of analytic continuation to obtain the weak form factors avoids the difficulty associated with the contribution from the nonvalence quark-antiquark pair creation. Our numerical results for the heavy-to-heavy and heavy-to-light meson decays are in a good agreement with the available experimental data and the lattice QCD results. In addition, our model predicts the two unmeasured mass spectra of $^{1}S_{0}(b\bar{b})$ and $^{3}S_{1}(b\bar{s})$ systems as $M_{b\bar{b}}$=9657 MeV and $M_{b\bar{s}}$= 5424 MeV.