What can a relativistic quark model tell us about charmed mesons?

A relativistic quark model is extended to incorporate chiral and gauge symmetries. We obtain the ${\mathit{DD}}^{\mathrm{*}}$π and ${\mathit{DD}}^{\mathrm{*}}$γ couplings and find that the ratio Γ(${\mathit{D}}^{\mathrm{*}0}$→${\mathit{D}}^0$ ${\mathrm{\pi }}^0$)/Γ(${\mathit{D}}^{\mathrm{*}0}$→${\mathit{D}}^0$γ) constrains the charm-quark mass close to 1.45 GeV. Large 1/${\mathit{m}}_{\mathit{c}}$ corrections appear in the heavy-quark contribution to the ${\mathit{DD}}^{\mathrm{*}}$γ coupling. The model is extended further to describe seven excited D meson states. We find that semileptonic B decays into the ground and excited D meson states do not account for the total semileptonic decay width of the ${\mathit{B}}^0$. The nonresonant contributions to the processes B${\mathrm{¯}}^0$→${\mathit{D}}^{\left(\mathrm{*}\right)}$πlν¯ appear to be large enough to account for the discrepancy.