MEASUREMENTS OF THE TAU-POLARIZATION IN Z(0) DECAYS

Journal article

A sample of Z0→τ+τ- events observed in the DELPHI detector at LEP in 1991 and 1992 is analysed to measure the τ polarisation in the exclusive decay channels {Mathematical expression}, {Mathematical expression}, πν, ρν and a1ν. The τ polarisation is also measured with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision than the use of the exclusive decay modes. The results have been combined with those published on the 1990 data. A measurement of the τ polarisation as a function of production angle yields the values for the mean τ polarisation 〈P〉τ=-0.148±0.022 and for the Z0 polarisation PZ=-0.136±0.027. These results are used to determine the ratio of vector to axial-vector effective couplings for taus {Mathematical expression}, and for electrons {Mathematical expression}, compatible with e-τ universality. With the assumption of lepton universality, the ratio of vector to axial-vector effective couplings for leptons {Mathematical expression} is obtained, implying a value of the effective weak mixing angle sin2θefflept=0.2320±0.0021 . © 1995 Springer-Verlag.

Authors: Abreu, P; Adam, W; Adye, T; Agasi, E; Ajinenko, I

• Publication status: Published
• Journal: ZEITSCHRIFT FUR PHYSIK C-PARTICLES AND FIELDS
• Volume: 67
• Issue: 2
• Pages: 183-201
• Publication date: 1995-06-01
• DOI: 10.1007/BF01571280
• EISSN: 1434-6052
• ISSN: 0170-9739
• Language: English