Properties of Hadronic Z-decays and Test of QCD Generators

Distributions are presented of event shape variables, jet roduction rates and charged particle momenta obtained from 53 000 hadronic Z decays. They are compared to the predictions of the QCD + hadronization models JETSET, ARIADNE and HERWIG, and are used to optimize several model parameters. The JETSET and ARIADNE coherent parton shower (PS) models with running alpha(s) and string fragmentation yield the best description of the data. The HERWIG parton shower model with cluster fragmentation fits the data less well. The data are in better agreement with JETSET PS than with JETSET O(alpha(s)2) matrix elements (ME) even when the renormalization scale is optimized.