Determination of the strong coupling αS from hadronic event shapes with O(\ensuremathαS3) and resummed QCD predictions using JADE data

Bowdery, Christopher and Foster, Frank and Hughes, Gareth (2009) Determination of the strong coupling αS from hadronic event shapes with O(\ensuremathαS3) and resummed QCD predictions using JADE data. European Physical Journal C: Particles and Fields, 64 (3). pp. 351-360. ISSN 1434-6044

Abstract

Event Shape Data from e+e− 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 \ensuremath\ensuremathαS(\ensuremathm\ensuremathZ0)=0.1210±0.0007\ensuremath(stat.)±0.0021\ensuremath(exp.)±0.0044\ensuremath(had.)±0.0036\ensuremath(theo.) and with the NNLO + NLLA calculations the combined value is \ensuremath\ensuremathαS(\ensuremathm\ensuremathZ0)=0.1172±0.0006\ensuremath(stat.)±0.0020\ensuremath(exp.)±0.0035\ensuremath(had.)±0.0030\ensuremath(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.