Dispersion Quark Model of Heavy Meson Decays

We discuss applications of the dispersion quark model to exclusive semileptonic decays of heavy mesons. The transition form factors in this relativistic formulation of the quark model are given by double spectral representations through the wave functions of the initial and final mesons both in the scattering and the decay regions. An important feature of the model is that the form factors have the correct behavior in accordance with QCD in the case of meson decays induced by heavy parent quark transition both to heavy and light daughter quarks. We demonstrate that the dispersion quark model gives results compatible with the lattice calculations at large $q^2$ and thus provides reliable form factors in the whole decay region.