A measurement of the QCD colour factors using event shape distributions atroot s=14 to 189 GeV

Measurements of the QCD colour factors C-A and C-F and of the number of act ive quark flavours n(f) in the process e(+)e(-) --> hadrons at high energy are presented. They are based on fits of O(alpha (2)(s)) + NLLA QCD calcula tions to distributions of the event shape observables 1 - T, C, B-T and B-W measured at centre-of-mass energies from 14 GeV to 189 GeV. Hadronisation effects are approximated with power correction calculations which also depe nd on the QCD gauge structure. In this approach potential biases from hadro nisation models are reduced. Our results for individually measured quantiti es obtained from 1 - T and C are n(f) = 5.64 +/- 1.35, C-A = 2.88 +/- 0.27 and C-F = 1.45 +/- 0.27 in good agreement with QCD based on the SU(3) symmetry group where n(f) = 5 for the energies considered here, C-A = 3 and C-F = 4/3. From simultaneous fits of C-A and C-F with 1 - T and C we find C-A = 2.84 +/- 0.24 and C-F = 1.29 +/- 0.18 which is also in good agreement with the QCD expectation.