Measurement of observables sensitive to coherence effects in hadronic Z decays with the OPAL detector at LEP

TL;DR

This paper investigates quantum chromodynamics (QCD) coherence effects in hadronic Z decays using four novel observables, comparing experimental data from OPAL at LEP with various parton shower models to understand their predictive accuracy.

Contribution

It introduces and measures four new observables sensitive to QCD coherence effects, comparing their experimental values with multiple parton shower models and ordering variables.

Findings

Experimental data show varying degrees of agreement with different models.

Dipole antenna models provide better predictions for certain observables.

Ordering variables significantly influence model predictions.

Abstract

A study of QCD coherence is presented based on a sample of about 397000 $e^+e^-$ hadronic annihilation events collected at $\sqrt{s}=91$ 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.