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Measurement of the Z resonance parameters at LEP

  • The ALEPH Collaboration
  • R. Barate et al.
Experimental physics

Abstract. The properties of the Z resonance are measured from the analysis of 4.5 million Z decays into fermion pairs collected with the Aleph detector at LEP. The data are consistent with lepton universality. The resonance parameters are measured to be \(M_{\rm Z}=(91.1885 \pm 0.0031){\rm GeV}/c^2\), \(\Gamma_{\rm Z}= (2.4951 \pm 0.0043)\) GeV, \(\sigma^0_{\rm had}=(41.559 \pm 0.058)\) nb and, combining the three lepton flavours, \(R_{\ell}= 20.725\pm 0.039\). The corresponding number of light neutrino species is \(N_{\nu}=2.983\pm0.013\) and the strong coupling constant is \(\alpha_s(M_{\rm Z}) = 0.114\pm{0.004} \pm 0.002_{\rm{QCD}} +\,0.005\,\log_{10}\left[\frac{M_{\rm H}}{150\,{\rm GeV}/c^2}\right]\,\). The lepton pair forward-backward asymmetry is measured to be \({\rm A}_{\rm FB}^{0, \ell}=0.0173 \pm 0.0016\) from which the effective weak mixing angle is derived: \(\sin^2\theta_{\rm eff}^{\rm lept} = 0.23089\pm 0.00089\). The measurement of the leptonic width \(\Gamma_{\ell\ell}=84.02\pm0.15\) MeV leads to a determination of the effective \(\rho\) parameter \(\rho_{\rm eff}^{\rm lept} = 1.0064 \pm 0.0018\). The data support the Standard Model and favour a light Higgs.

Keywords

Strong Coupling Effective Parameter Resonance Parameter Light Neutrino Lepton Pair 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • The ALEPH Collaboration
  • R. Barate et al.
    • 1
  1. 1.Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, 74019 Annecy-le-Vieux Cedex, France FR

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