Determination of {\alpha}S using OPAL hadronic event shapes at sqrt(s) = 91 - 209 GeV and resummed NNLO calculations

TL;DR

This paper measures the strong coupling constant {}S using OPAL e+e- annihilation data across energies 91-209 GeV, employing advanced NNLO and NNLO+NLLA QCD calculations to improve precision and confirm QCD predictions of asymptotic freedom.

Contribution

It provides the first determination of {}S using NNLO and NNLO+NLLA calculations across a wide energy range, enhancing the accuracy of QCD tests.

Findings

{}S at Z boson mass: 0.1201 b1 0.0024 (theo.)

Energy dependence of {}S confirms asymptotic freedom

Improved theoretical precision over previous NLO-based results

Abstract

Hadronic event shape distributions from e+e- annihilation measured by the OPAL experiment at centre-of-mass energies between 91 GeV and 209 GeV are used to determine the strong coupling {\alpha}S. The results are based on QCD predictions complete to the next-to- next-to-leading order (NNLO), and on NNLO calculations matched to the resummed next-to-leading-log-approximation terms (NNLO+NLLA). The combined NNLO result from all variables and centre-of-mass energies is {\alpha}S(mZ0) = 0.1201 {\pm} 0.0008(stat.) {\pm} 0.0013(exp.) {\pm} 0.0010(had.) {\pm} 0.0024(theo.). while the combined NNLO+NLLA result is {\alpha}S(mZ0) = 0.1189 {\pm} 0.0008(stat.) {\pm} 0.0016(exp.) {\pm} 0.0010(had.) {\pm} 0.0036(theo.). The completeness of the NNLO and NNLO+NLLA results with respect to missing higher order contributions, studied by varying the renormalization scale, is improved compared to previous results based on NLO or NLO+NLLA predictions only. The observed energy dependence of {\alpha}S agrees with the QCD prediction of asymptotic freedom and excludes the absence of running.