DECAMP, D (reprint author), CNRS, IN2P3, LAB PHYS PARTICULES LAPP, F-74019 ANNECY LE VIEUX, FRANCE.
Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant alpha-s is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust. C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles are first combined in clusters using a minimum scaled invariant mass cut, y(cut), before these variables are computed. The combined result from all shape variables of pre-clustered events is alpha-s(M(Z)2) = 0.117 +/- 0.005 for a renormalization scale mu = 1/2M(Z). For mu-values between M(Z) and the b-quark mass, the result changes by -0.009(+0.006).