Experimental studies on multijet production in e+e- annihilation at PETRA energies

TLDR: In this article, the authors compared 2nd-order QCD calculations with 3-and 4-jet models in the energy range of 14.0-46.7 GeV and showed that the observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions.

Abstract: Hadronic jet production bye+e−-annihilation has been studied in the energy range of 14.0–46.7 GeV. The data have been analysed in terms of a cluster algorithm and other topological quantities. The results are compared with 2nd order QCD calculations which incorporate models for the fragmentation of quarks and gluons into hadrons. At the higher energies we observe more spherical and 4-jet like events than predicted by these calculations. We cannot achieve a simultaneous description of the observed 3- and 4-jet production by adjusting the strong coupling constant αs or the fragmentation parameters of the 2nd order QCD models. The observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions. Consequences of the presented results for the value of αs, determined in previous analyses, are discussed. QCD parton shower models, including soft gluon interference, are able to describe the observed number of spherical events.