Studies of jet production rates and tests of QCD on the Z0 resonance

In this paper production rates of multi-jet hadronic final states of Z0 boson decays are studied. They can be well described by analytic O(αs2) QCD calculations with parameters are determined at lower energies. The data cannot be described by an abelian, QED-like vector gluon model. The QCD parameters ΛbarMS and μ2 are adjusted to describe the measured differential 2-jet invariant mass distribution. In second order QCD, including theoretical uncertainties due to the ambiguous choice of the renormalization scale μ2, the result is Λ(5)/MS = (80 - 450) MeV, which corresponds to αs(MZ0) = 0.117 ± 0.015. Significant scaling violations are observed when the 3-jet fractions are compared to the corresponding results from smaller center of mass energies, thus increasing, in good agreement with QCD, the evidence for a running coupling constant αs