Measurement of event shape distributions and moments in e+e- -> hadrons at 91-209 GeV and a determination of alphas
The OPAL Collaboration, G. Abbiendi
Abstract
We have studied hadronic events from e+e- annihilation data at centre-of-mass energies from 91 to 209 GeV. We present distributions of event shape observables and their moments at each energy and compare with QCD Monte Carlo models. From the event shape distributions we extract the strong coupling alphas and test its evolution with energy scale. The results are consistent with the running of alphas expected from QCD. Combining all data, the value of alphas(MZ) is determined to be alphas(MZ) = 0.1191 +- 0.0005 (stat.) +- 0.0010 (expt.) +- 0.0011 (hadr.) +- 0.0044 (theo.). The energy evolution of the moments is also used to determine a value of alphas with slightly larger errors: alphas(MZ) = 0.1223 +- 0.0005 (stat.) +- 0.0014 (expt.) +- 0.0016 (hadr.) +0.0054 -0.0036 (theo.).
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