QCD Analyses and determinations of alpha-s in e+e- Annihilation at energies between 35 and 189 GeV

TL;DR

This paper analyzes e+e- annihilation data from 35 to 189 GeV to measure the strong coupling constant alpha_s using jet observables and compares various theoretical predictions, providing a precise determination of alpha_s(MZ).

Contribution

It provides a comprehensive QCD analysis across a wide energy range, comparing multiple theoretical models and extracting alpha_s with improved accuracy and understanding of scale dependence.

Findings

Alpha_s(MZ)=0.1187+0.0034-0.0019 from combined fits.

Consistent results across different jet algorithms and energy scales.

Comparison of matching schemes and scale dependence enhances theoretical understanding.

Abstract

We employ data taken by the JADE and OPAL experiments for an integrated QCD study in hadronic e+e- annihilations at c.m.s. energies ranging from 35 GeV through 189 GeV. The study is based on jet-multiplicity related observables. The observables are obtained to high jet resolution scales with the JADE, Durham, Cambridge and cone jet finders, and compared with the predictions of various QCD and Monte Carlo models. The strong coupling strength, alpha_s, is determined at each energy by fits of O(alpha_s^2) calculations, as well as matched O(alpha_s^2) and NLLA predictions, to the data. Matching schemes are compared, and the dependence of the results on the choice of the renormalization scale is investigated. The combination of the results using matched predictions gives alpha_s(MZ)=0.1187+{0.0034}-{0.0019}. The strong coupling is also obtained, at lower precision, from O(alpha_s^2) fits of the c.m.s. energy evolution of some of the observables. A qualitative comparison is made between the data and a recent MLLA prediction for mean jet multiplicities.