Measurement of the Strong Coupling alpha s from Four-Jet Observables in e+e- Annihilation

TL;DR

This paper measures the strong coupling constant alpha_s using four-jet observables in electron-positron annihilation data from LEP, achieving results consistent with the world average and exploring additional event-shape observables.

Contribution

It provides a precise measurement of alpha_s from four-jet rates and introduces the first NLO fits to D-parameter and thrust minor observables.

Findings

Measured alpha_s(Mz)=0.1182 with uncertainties.

First NLO fits to D-parameter and thrust minor.

Results agree with the world average.

Abstract

Data from e+e- annihilation into hadrons at centre-of-mass energies between 91 GeV and 209 GeV collected with the OPAL detector at LEP, are used to study the four-jet rate as a function of the Durham algorithm resolution parameter ycut. The four-jet rate is compared to next-to-leading order calculations that include the resummation of large logarithms. The strong coupling measured from the four-jet rate is alphas(Mz0)= 0.1182+-0.0003(stat.)+-0.0015(exp.)+-0.0011(had.)+-0.0012(scale)+-0.0013(mass) in agreement with the world average. Next-to-leading order fits to the D-parameter and thrust minor event-shape observables are also performed for the first time. We find consistent results, but with significantly larger theoretical uncertainties.