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Measurement of electroweak parameters from Z decays into Fermion pairs

Research output: Contribution to journalJournal article


  • ALEPH Collaboration
<mark>Journal publication date</mark>1990
<mark>Journal</mark>Zeitschrift für Physik C Particles and Fields
Issue number3
Number of pages27
Pages (from-to)365-391
<mark>Original language</mark>English


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 had 0=(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 v 2(M Z 2)=(0.12±0.12)×10−2 andg A 2(M Z 2)=0.2528±0.0040. The number of light neutrino species isN ν=2.91±0.13; the electroweak mixing angle is sin2θW(M Z 2)=0.2291±0.0040.