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Update of electroweak parameters fromZ decays

Research output: Contribution to journalJournal article

Published

Journal publication date1993
JournalZeitschrift für Physik C: Particles and Fields
Journal number1
Volume60
Number of pages12
Pages71-81
Original languageEnglish

Abstract

Based on 520 000 fermion pairs accumulated during the first three years of data collection by the ALEPH detector at LEP, updated values of the resonance parameters of theZ are determined to beMZ=(91.187±0.009) GeV, ΓZ=(2.501±0.012) GeV, σhad0=(41.60±0.27) nb, andRℓ=20.78±0.13. The corresponding number of light neutrino species isNν=2.97±0.05. The forward-backward asymmetry in lepton-pair decays is used to determine the ratio of vector to axial-vector couplings of leptons:gV2(MZ2)/gA2(MZ2)=0.0052±0.0016. Combining this with ALEPH measurements of theb andc quark asymmetries and τ polarization gives sin2θWeff=0.2326±0.0013. Assuming the minimal Standard Model, and including measurements ofMW/MZ frompp ¯ colliders and neutrino-nucleon scattering, the mass of the top quark isM top =156±22 25 ±17 22Higgs GeV.