A METHOD TO DETERMINE THE ELECTROWEAK MIXING ANGLE FROM Z-DECAYS TO TAU-LEPTONS USING OPTIMAL OBSERVABLES

We propose a new method to measure the electroweak mixing angle in Z d ecays to tau leptons. For various tau decay channels optimal observabl es are constructed which yield the largest possible signal-to-noise ra tio. These optimal observables are derived from the full spin-density- matrix of the process including correlations between tau spins and an approximation to the tau flight direction.