ISSN:
1434-6052
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract 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 $$ev\bar v$$ , $$\mu v\bar v$$ , 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 polarisationP Z=−0.136±0.027. These results are used to determine the ratio of vector to axial-vector effective couplings for taus $$\bar v_\tau /\bar a_\tau = 0.074 \pm 0.011$$ , and for electrons $$\bar v_e /\bar a_e = 0.068 \pm 0.014$$ , compatible with e-τ universality. With the assumption of lepton universality, the ratio of vector to axial-vector effective couplings for leptons $$\bar v_l /\bar a_l = 0.072 \pm 0.008$$ is obtained, implying a value of the effective weak mixing angle sin2θ eff lept =0.2320±0.0021.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01571280
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