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

نویسندگان

  • S. Bethke
  • S. Kluth
چکیده

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.

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تاریخ انتشار 2008