Determination of the Strong Coupling αS from hadronic Event Shapes and NNLO QCD predictions using JADE Data

Event Shape Data from ee annihilation into hadrons collected by the JADE experiment at centre-of-mass energies between 14 GeV and 44 GeV are used to determine the strong coupling αS. QCD predictions complete to next-to-next-to-leading order (NNLO), alternatively combined with resummed next-to-leading-log-approximation (NNLO+NLLA) calculations, are used. The combined value from six different event shape observables at the six JADE centre-of-mass energies using the NNLO calculations is αS(mZ0) = 0.1210 ± 0.0007(stat.) ± 0.0021(exp.) ± 0.0044(had.) ± 0.0036(theo.) and with the NNLO+NLLA calculations the combined value is αS(mZ0) = 0.1172 ± 0.0006(stat.) ± 0.0020(exp.) ± 0.0035(had.) ± 0.0030(theo.) . The stability of the NNLO and NNLO+NLLA results with respect to missing higher order contributions, studied by variations of the renormalisation scale, is improved compared to previous results obtained with NLO+NLLA or with NLO predictions only. The observed energy dependence of αS agrees with the QCD prediction of asymptotic freedom and excludes absence of running with 99% confidence level.