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Update of electroweak parameters fromZ decays

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Zeitschrift für Physik C Particles and Fields

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 beM Z =(91.187±0.009) GeV, Γ Z =(2.501±0.012) GeV, σ 0had =(41.60±0.27) nb, andR =20.78±0.13. The corresponding number of light neutrino species isN ν=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:g 2 V (M 2 Z )/g 2 A (M 2 Z )=0.0052±0.0016. Combining this with ALEPH measurements of theb andc quark asymmetries and τ polarization gives sin2θ eff W =0.2326±0.0013. Assuming the minimal Standard Model, and including measurements ofM W /M Z fromp \(\bar p\) colliders and neutrino-nucleon scattering, the mass of the top quark is\(M_{top} = 156 \pm \begin{array}{*{20}c} {22} \\ {25} \\ \end{array} \pm \begin{array}{*{20}c} {17} \\ {22Higgs} \\ \end{array} \) GeV.

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Deceased

Supported by CICYT, 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 DE-AC02-76ER00881

Supported by the US Department of Energy, contract DE-FG05-87ER40319

Supported by the NSF, contract PHY-8451274

Supported by the US Department of Energy, contract DE-FC0S-85ER250000

Supported by SLOAN fellowship, contract BR2703

Supported by the Bundesministerium für Forschung und Technologie, Germany

Supported by the Direction des Sciences de la Matière, C.E.A.

Supported by Fonds zur Förderung der wissenschaftlichen Forschung, Austria

Supported by the Korean Science and Engineering Foundation and Ministry of Education

Supported by the US Department of Energy, grant DE-FG03-92 ER40689

Partially supported by Colciencias, Colombia

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ALEPH Collaboration., Buskulic, D., Decamp, D. et al. Update of electroweak parameters fromZ decays. Z. Phys. C - Particles and Fields 60, 71–81 (1993). https://doi.org/10.1007/BF01650432

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