Abstract
A study of QCD coherence is presented based on a sample of about 397,000 e+e- hadronic annihilation events collected at √ s = 91 GeV with the OPAL detector at LEP. The study is based on four recently proposed observables that are sensitive to coherence effects in the perturbative regime. The measurement of these observables is presented, along with a comparison with the predictions of different parton shower models. The models include both conventional parton shower models and dipole antenna models. Different ordering variables are used to investigate their influence on the predictions.
Highlights
In the evolution of a hard hadronic interaction to a final state observable in experiment the concept of the parton shower plays an important role
All observables are constructed to be sensitive to coherence effects and other properties of the parton shower models
In general we find that all models give a fair description of the data measured by OPAL
Summary
In the evolution of a hard hadronic interaction to a final state observable in experiment the concept of the parton shower plays an important role. The main ingredient of the parton shower is that a hard parton transforms into a jet by repeatedly radiating gluons, which themselves can radiate, or create a quark-antiquark-pair, creating an avalanche or shower of partons. This process is regulated by colour coherence, i.e. the destructive interference of multiple colour-connected soft gluon emissions. In [2] new observables based on e+e− annihilation into hadrons are proposed and studied to investigate differences between parton shower models. These new observables were shown to have sensitivity to explore differences between parton shower models and a measurement with data from the OPAL experiment at LEP was performed [3]
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