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 Afb in the reaction B¯→D*l-ν¯l using data collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR). The value of Afb 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 Afb and the previously determined branching ratio, q2 distribution, and D* polarization, we obtain the first measurement of the form-factor ratios that are used to describe this semileptonic decay.