Constraints on semileptonic B decays from the measurement of the D/emph> polarization in B→D/emph>eν¯

Abstract

The rates for the decays B→Deν¯ and B→$D^{\mathrm{*}}$eν¯ are calculated, with emphasis on the consequences of approximate flavor independence of the meson wave functions. We find that one of the form factors is not easily constrained so that the result for the $D^{\mathrm{*}}$ final state is uncertain. However, a recent measurement of the average polarization of the $D^{\mathrm{*}}$ from B→$D^{\mathrm{*}}$eν¯ can be used to constrain this form factor. Implications for the determination of the Kobayashi-Maskawa matrix element $V_{\mathrm{cb}}$ are discussed.