Excited charm mesons in semileptonicB¯decay and their contributions to a Bjorken sum rule

Abstract

It has recently been shown that hadrons containing a single heavy quark exhibit a new flavor-spin symmetry of QCD. We exploit this symmetry to obtain model-independent predictions for the 14 form factors in weak decays from the ground-state pseudoscalar meson $P_{Q_i}$ of a heavy quark $Q_i$ to the low-lying positive-parity excited states of a heavy quark $Q_j$ in terms of two universal functions of momentum transfer. These predictions are of interest in the study of $\overline{B}\to D_2^{*}\mathrm{}\left(2460\right), D_1\mathrm{}\left(2420\right), D_1\left(\sim 2360\right), \mathrm{and} D_0^{*}\left(\sim 2360\right)$ semileptonic decays. We also discuss the connection between these results and the slope of the function $\xi$ (which determines the $\overline{B}\to D$ and $\overline{B}\to D^{*}$ transition form factors) given by a heavy-quark sum rule suggested by Bjorken.