Measurement of τ polarisation at LEP

This is the authors' abstract. We don't add key points for this paper.

Using the data collected with the L3 detector at LEP between 1990 and 1995, corresponding to an integrated luminosity of 149 pb−1, the τ longitudinal polarisation has been measured as a function of the production polar angle using the τ decays τ−→h−ντ (h=π,ρ,a1) and τ−→ℓ−ν̄ℓντ (ℓ=e,μ). From this measurement the quantities Ae and Aτ, which depend on the couplings of the electron and the τ to the Z, are determined to be Ae=0.1678±0.0127±0.0030 and Aτ=0.1476±0.0088±0.0062, consistent with the hypothesis of e–τ universality. Under this assumption a value of Aℓ=0.1540±0.0074±0.0044 is obtained, yielding the value of the effective weak mixing angle sin2θW=0.2306±0.0011.