2021 Impact factor 4.991
Particles and Fields

Eur. Phys. J. C 20, 601-615 (2001)
DOI: 10.1007/s100520100699

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

The OPAL Collaboration G. Abbiendi and et al.

Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

(Received: 11 January 2001 / Published online: 29 June 2001 -© Springer-Verlag / Società Italiana di Fisica 2001)

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, CF and CA, 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,

\begin{displaymath}C_A=3.02\pm 0.25\mathrm{(stat.)} \pm
0.49\mathrm{(syst.)} ,
C_F=1.34\pm 0.13\mathrm{(stat.)} \pm
0.22\mathrm{(syst.)} ,

\begin{displaymath}\alpha_s (M_Z)=0.120\pm 0.011\mathrm{(stat.)}
0.020\mathrm{(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 CF and CA and the world average of $\alpha_s(M_{Z})$.

© Società Italiana di Fisica, Springer-Verlag 2001