Tests of models of color reconnection and a search for glueballs using gluon jets with a rapidity gap.

摘要

Gluon jets are selected from hadronic Z0 decay events produced in e+e− annihilations. A subsample of these jets is identified which exhibits a large gap in the rapidity distribution of particles within the jet. These jets are observed to demonstrate a high degree of sensitivity to the presence of color reconnection, i.e. higher order QCD processes affecting the underlying color structure. We use our data to test three QCD models which include a simulation of color reconnection: one in the Ariadne Monte Carlo, one in the Herwig Monte Carlo, and the other by Rathsman in the Pythia Monte Carlo. We conclude that color reconnection as implemented by the Rathsman and Ariadne models is disfavored. The signal from the Herwig color reconnection model is less clear and we do not obtain a definite conclusion concerning this model. In a separate study, we follow recent theoretical suggestions and search for glueball-like objects in the leading part of the gluon jets. No clear evidence is observed for these objects.