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Measurement of the tau polarization at the Z resonance

Research output: Contribution to journalJournal article


  • ALEPH Collaboration
<mark>Journal publication date</mark>1993
<mark>Journal</mark>Zeitschrift für Physik C Particles and Fields
Issue number3
Number of pages18
Pages (from-to)369-386
<mark>Original language</mark>English


Using 18.8 pb−1 of data collected in 1990 and 1991, ALEPH has measured the tau polarisation in the decay modes τ→ev vˉ , τ→μv vˉ , τ→πν, τ→ρν and τ→a 1ν, using both the individual tau decay kinematics and the event acollinearity. The measurement of the tau polarisation as a function of the production polar angle yields the two parametersA τ andA e , whereA l =2g v l g A l /(g v l )2+(g A l )2] The resultsA τ=0.143±0.023 andA e =0.120±0.026 are consistent with the hypothesis of electron-tau universality. Assuming universality yields a measurement of the effective weak mixing angle sin2θ w eff=0.2332±0.0022.