Semileptonic, radiative, and pionic decays of B,B* and D,D* mesons.

Abstract

A relativistic constituent quark model (RQM) is used to calculate the form factors for the semileptonic decays B, D\ensuremath{\rightarrow}\ensuremath{\pi}(\ensuremath{\rho})l\ensuremath{\nu}, B\ensuremath{\rightarrow}D(${\mathit{D}}^{\mathrm{*}}$)l\ensuremath{\nu}, D\ensuremath{\rightarrow}K(${\mathit{K}}^{\mathrm{*}}$)l\ensuremath{\nu}, and the coupling constants for the radiative decays ${\mathit{B}}^{\mathrm{*}}$\ensuremath{\rightarrow}B\ensuremath{\gamma}, ${\mathit{D}}^{\mathrm{*}}$\ensuremath{\rightarrow}D\ensuremath{\gamma}. The quark model is combined with a soft pion theorem to derive the ${\mathit{B}}^{\mathrm{*}}$B\ensuremath{\pi} and ${\mathit{D}}^{\mathrm{*}}$D\ensuremath{\pi} coupling constants, which are used to calculate the rate for ${\mathit{D}}^{\mathrm{*}}$\ensuremath{\rightarrow}D\ensuremath{\pi}. The parameters of the model are fixed by exploiting the duality of the vector meson dominance (VMD) picture and the picture of constituent quarks. This approach, which requires only that the predictions of the VMD model and the RQM are consistent, enables a parameter free determination of heavy quark properties, and leads to a ${\mathit{q}}^{2}$ dependence of form factors which is different from the usual pole approximation. The predicted rates for D and ${\mathit{D}}^{\mathrm{*}}$ mesons agree with the data without exception. This positive result supports the conclusion that properties of heavy mesons can be analyzed consistently in this framework. \textcopyright{} 1996 The American Physical Society.