Measurement of the tau lepton polarization and its forward-backward asymmetry from Z0 decays

Abstract

We report on a measurement of the tau lepton polarization and its forward-backward asymmetry at the Z0 resonance using the OPAL detector. This measurement is based on analyses of the {Mathematical expression}, {Mathematical expression}, τ→π(K)vτ and τ→ρvτ from a sample of 30663 e+e+→τ+τ- events collected during the years 1990 to 1992. Assuming that the tau lepton decays according to V-A theory, we measure the average τ polarization to be =(-14.9±1.9±1.3)% and the τ polarization forward-backward asymmetry to be Apol FB=(-8.9±2.2±0.9)%, where the first error is statistical and the second systematic. These results are consistent with the hypothesis of lepton universality. When combined unde..