Lepton asymmetry measurements in B¯→D*l−ν¯l and implications for V-A and the form factors

Abstract

We present a measurement of the lepton decay asymmetry ${\mathit{A}}_{\mathrm{fb}}$ in the reaction B¯→${\mathit{D}}^{\mathrm{*}}$ ${\mathit{l}}^{\mathrm{-}}$ν${\mathrm{¯}}_{\mathit{l}}$ using data collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR). The value of ${\mathit{A}}_{\mathrm{fb}}$ confirms that the chirality of the weak interaction is predominantly left-handed in b→c transitions as expected in the standard model, if it is assumed that the lepton current is also left-handed. Using ${\mathit{A}}_{\mathrm{fb}}$ and the previously determined branching ratio, ${\mathit{q}}^2$ distribution, and ${\mathit{D}}^{\mathrm{*}}$ polarization, we obtain the first measurement of the form-factor ratios that are used to describe this semileptonic decay.