Electroweak tests with τ leptons at LEP

Abstract

We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z0 pole. From measurements of the τ polarization in e+ e−→τ+τ−, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to begve/gae=0.066±0.015 andgVτ/gAτ=0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beGτ/Gμ=0.996±0.008.