Abstract:

I present a study of the exclusive semileptonic -meson decay carried out by the CLEO collaboration.I fully reconstruct the and charged lepton and determine the angle between the decaying -meson and the combination.I present a prelimnary measurement of the branching ratio obtained through a fit to the distribution of this angle.This fit separates our signal decay mode from other decays involving higher resonance states or additional hadrons in the final state.I discuss the important systematics errors in this analysis, in particular the slow pion tracking efficiency.Finally, I present the technique which will be used to extract the CKM matrix element with similar methods, and I give the status of that work.This analysis uses a data sample of 3.3 million events collected with the CLEO II detector at the Cornell Electron Storage Ring.