OPAL measurements of the tau polarization and forward-backward polarization asymmetry near the Z resonance are described. The measurements are based on analyses of tau decays into e nu_e nu_tau, mu nu_mu nu_tau, pi nu_tau,rho nu_tau and a1 nu_tau final states from a sample of 144810 tau-tau candidates. The integrated luminosity is 151 pb-1. Assuming tau decays according to V-A theory, we measure the average tau polarization and the tau polarization forward-backward asymmetry. Taking into account the small effects of the photon propagator, photon-Z interference and photonic radiative corrections, these results can be expressed in terms of the lepton neutral current (NC) asymmetry parameters Atau and Ae. These measurements are consistent with lepton universality and combine to give Al=0.1455+-0.0073. Within the context of the SM this orresponds to sin^2(theta)(lept,eff)=0.23172+-0.00092. A combination with other OPAL NC measurements yields sin^2(theta)(lept,eff)=0.23211+-0.00068.



Stefan Soldner-Rembold
2001-05-14