Subleading Isgur-Wise form factors from QCD sum rules.

Abstract

In the heavy-quark effective theory, current matrix elements between two heavy pseudoscalar or vector mesons are parametrized by a set of universal form factors. These functions are calculated to subleading order in the $\frac{1}{{m}_{Q}}$ expansion using QCD sum rules. The equations of motion and Ward identities of the effective theory are incorporated in the analysis. Within this approach, parameter-free predictions are obtained for all form factors at zero recoil. The results allow for an almost model-independent analysis of current-induced transitions between heavy mesons. As an application, the $\frac{1}{{m}_{c}}$ and $\frac{1}{{m}_{b}}$ corrections to the hadronic form factors describing semileptonic $B\ensuremath{\rightarrow}D\ensuremath{\ell}\ensuremath{\nu}$ and $B\ensuremath{\rightarrow}{D}^{*}\ensuremath{\ell}\ensuremath{\nu}$ decays are computed. The possibility of extracting ${V}_{\mathrm{cb}}$ from these processes is discussed, and the importance of a measurement of symmetry-violating effects in ratios of form factors is pointed out.