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Measurement of electroweak parameters fromZ decays into fermion pairs

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Zeitschrift für Physik C Particles and Fields

Abstract

We report on the properties of theZ resonance from 62 500Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We findM Z=(91.193±0.016exp±0.030LEP) GeV, Γ Z =(2497±31) MeV, σ 0had =(41.86±0.66)nb, and for the partial widths Γinv=(489±24) MeV, Γhad(1754±27) MeV, Γ ee =(85.0±1.6)MeV, Γ μμ =(80.0±2.5) MeV, and Γττ=(81.3±2.5) MeV, all in good agreement with the Standard Model. Assuming lepton universality and using a lepton sample without distinction of the final state we measure Γu=(84.3±1.3) MeV. The forward-backward asymmetry in leptonic decays is used to determine the vector and axial-vector weak coupling constants of leptors,g 2v (M 2 Z )=(0.12±0.12)×10−2 andg 2A (M 2 Z )=0.2528±0.0040. The number of light neutrino species isN ν=2.91±0.13; the electroweak mixing angle is sin2θW(M 2Z )=0.2291±0.0040.

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Now at CERN

Supported by CAICYT, Spain

Supported by the National Science Foundation of China

Supported by the Danish Natural Science Research Council

Supported by the UK Science and Engineering Research Council

Supported by the US Department of Energy, contract DEAC02-76ER00881

Supported by the US Department of Energy, contract DEFG05-87ER40319

Supported by the NSF, contract PHY-8451274

Supported by the US Department of Energy, contract DEFC0S-85ER250000

Supported by SLOAN fellowship, contract BR 2703

Supported by the Bundesministerium für Forschung und Technologie, FRG

Supported by the Institut de Recherche Fondamentale du C.E.A.

Supported by Fonds zur Förderung der wissenschaftlichen Forschung, Austria

Supported by Non Directed Research Fund, Korea Res. Found., 1989

On leave of absence from SLAC, Stanford, CA 94309, USA

On leave of absence from University of Washington, Seattle, WA 98195, USA

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ALEPH Collaboration., Decamp, D., Deschizeaux, B. et al. Measurement of electroweak parameters fromZ decays into fermion pairs. Z. Phys. C - Particles and Fields 48, 365–391 (1990). https://doi.org/10.1007/BF01572019

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  • DOI: https://doi.org/10.1007/BF01572019

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