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Measurements of the strong coupling constant and the QCD colour factors using four-jet observables from hadronic Z decays

  • The ALEPH Collaboration
  • A. Heister et al.
Experimental Physics

Abstract.

Data from \({\rm e^+e^-}\) annihilation into hadrons, taken with the ALEPH detector at the Z resonance, are analyzed. The four-jet rate is studied as a function of the resolution parameter and compared to next-to-leading order calculations combined with resummation of large logarithms. Angular correlations in four-jet events are measured and compared to next-to-leading order QCD predictions. With these observables two different measurements are performed. In a first analysis the strong coupling constant is measured from the four-jet rate yielding \(\alpha_s(M_{\mathrm Z}) = 0.1170 \pm 0.0001 ({\rm stat}) \pm 0.0013 ({\rm sys})\) . In a second measurement the strong coupling constant and the QCD colour factors are determined simultaneously from a fit to the four-jet rate and the four-jet angular correlations, giving \(\alpha_s(M_{\rm Z}) = 0.119 \pm 0.006 ({\rm stat}) \pm 0.026 ({\rm sys})\) \(C_{\rm A} = 2.93 \pm 0.14 ({\rm stat}) \pm 0.58 ({\rm sys})\) \(C_{\rm F} = 1.35 \pm 0.07 ({\rm stat}) \pm 0.26 ({\rm sys})\) in good agreement with the expectation from QCD.

Keywords

Strong Coupling Angular Correlation Colour Factor Resolution Parameter Large Logarithm 
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 / Società Italiana di Fisica 2003

Authors and Affiliations

  • The ALEPH Collaboration
  • A. Heister et al.
    • 1
  1. 1.Physikalisches Institut das RWTH-Aachen, 52056 Aachen, Germany DE

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