Weak decays in the light-front quark model

We study the form factors of heavy-to-heavy and heavy-to-light weak decays using the light-front relativistic quark model. For the heavy-to-heavy B→${\mathit{D}}^{\left(\mathrm{*}\right)}$ semileptonic decays we calculate the corresponding Isgur-Wise function for the while kinematic region. For the heavy-to-light B→P and B→V semileptonic decays we calculate the form factors at ${\mathit{q}}^2$=0; in particular, we have derived the dependence of the form factors on the b-quark mass in the ${\mathit{m}}_{\mathit{b}}$→∞ limit. This dependence cannot be produced by extrapolating the scaling behavior of the form factors at ${\mathit{q}}_{\max }^2$ using the single-pole assumption. This shows that the ${\mathit{q}}^2$ dependence of the form factors in regions far away from the zero recoil could be much more complicated than that predicted by the single-pole assumption.