Tests of Power Corrections for Event Shapes in e+e- Annihilation

TL;DR

This paper combines perturbative QCD calculations with power corrections to accurately model hadronisation effects in e+e- annihilation, fitting data across a wide energy range to measure fundamental parameters and test universality.

Contribution

It introduces a comprehensive analysis of event shape observables using combined QCD and power correction models, confirming the universality of the power correction parameter alpha_0.

Findings

Good agreement between QCD predictions and data for multiple observables.

Precise measurements of alpha_S(M_Z) and alpha_0(2 GeV).

Confirmation of the universality of alpha_0 within uncertainties.

Abstract

A study of perturbative QCD calculations combined with power corrections to model hadronisation effects is presented. The QCD predictions are fitted to differential distributions and mean values of event shape observables measured in e+e- annihilation at centre-of-mass energies from 14 to 189 GeV. We investigate the event shape observables thrust, heavy jet mass, C-parameter, total and wide jet broadening and differential 2-jet rate and observe a good description of the data by the QCD predictions. The strong coupling constant alpha_S(M_Z) and the free parameter of the power correction calculations alpha_0(2 GeV) are measured to be alpha_S(M_Z) = 0.1171 +/- 0.0032/0.0020 and alpha_0(2 GeV) = 0.513 +/- 0.066/0.045. The predicted universality of alpha_0 is confirmed within the uncertainties of the measurements.