A simultaneous measurement of the QCD colour factors and the strong coupling

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Using data from e(+)e(-) annihilation into hadrons, taken with the OPAL detector at LEP at the Z pole between 1991 and 1995, we performed a simultaneous measurement of the colour factors of the underlying gauge group of the strong interaction, C-F and C-A, and the strong coupling, alpha (s). The measurement was carried out by fitting next-to-leading order perturbative predictions to measured angular correlations of 4-jet events together with multi-jet related variables. Our results, C-A = 3.02 +/- 0.25(stat.) +/- 0.49(syst.), CF = 1.34 +/- 0.13(stat.) +/- 0.22(syst.), alpha (s) (M-Z) = 0.120 +/- 0.011(stat.) +/- 0.020(syst,), provide a test of perturbative QCD in which the only assumptions are non-abelian gauge symmetry and standard hadronization models. The measurements are in agreement with SU(3) expectations for C-F and C-A and the world average of alpha (s)(M-Z).


Original languageEnglish
Pages (from-to)601-615
Number of pages15
JournalEuropean Physical Journal C
Issue number4
Publication statusPublished - 1 May 2001