Measurement of the Michel parameters in leptonic tau decays

OPAL Collaboration (1999) Measurement of the Michel parameters in leptonic tau decays. European Physical Journal C: Particles and Fields, 8 (1). pp. 3-21. ISSN 1434-6044

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The Michel parameters of the leptonic ττ decays are measured using the OPAL detector at LEP. The parameters ρℓρℓ , ξℓξℓ , (ξδ)ℓ(ξδ)ℓ (with ℓ=e,μℓ=e,μ ) and ημημ are extracted from the energy spectra of the charged decay leptons and from their energy–energy correlations. A new method involving a global likelihood fit of Monte Carlo generated events with complete detector simulation and background treatment has been applied to the data recorded at center-of-mass energies close to s√=mZ0s=mZ0 corresponding to an integrated luminosity of 155 pb −1−1 . If e- μμ universality is assumed and inferring the ττ polarization from neutral current data, the measured Michel parameters are: where the value of ηη has been constrained using the published OPAL measurements of the leptonic branching ratios and the ττ lifetime. Limits on non-standard coupling constants and on the masses of new gauge bosons are obtained. The results are in agreement with the V–A prediction of the Standard Model.

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Journal Article
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European Physical Journal C: Particles and Fields
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02 Nov 2016 16:54
Last Modified:
19 Sep 2023 01:40