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

Abstract

A relativistic quark model is extended to incorporate chiral and gauge symmetries. We obtain the ${\mathit{DD}}^{\mathrm{*}}$\ensuremath{\pi} and ${\mathit{DD}}^{\mathrm{*}}$\ensuremath{\gamma} couplings and find that the ratio \ensuremath{\Gamma}(${\mathit{D}}^{\mathrm{*}0}$\ensuremath{\rightarrow}${\mathit{D}}^{0}$${\mathrm{\ensuremath{\pi}}}^{0}$)/\ensuremath{\Gamma}(${\mathit{D}}^{\mathrm{*}0}$\ensuremath{\rightarrow}${\mathit{D}}^{0}$\ensuremath{\gamma}) constrains the charm-quark mass close to 1.45 GeV. Large 1/${\mathit{m}}_{\mathit{c}}$ corrections appear in the heavy-quark contribution to the ${\mathit{DD}}^{\mathrm{*}}$\ensuremath{\gamma} 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${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$\ensuremath{\rightarrow}${\mathit{D}}^{(\mathrm{*})}$\ensuremath{\pi}l\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{} appear to be large enough to account for the discrepancy.