Determination of alpha_S using hadronic event shape distributions of data taken with the OPAL detector

Abstract

The measurement of the strong coupling alpha_S using hadronic event shape distributions measured with the OPAL detector at center-of-mass energies between 91 and 209 GeV is summarized. For this measurement hadronic event shape distributions are compared to theoretical predictions based on next-to-next-to-leading-calculations (NNLO) and NNLO combined with resummed next-to-leading-logarithm calculations (NLLA). The combined result using NNLO calculations is alpha_S(MZ)=0.1201+-0.0008(stat.)+-0.0013(exp.)+-0.0010(had.)+-0.0024(theo.) and the result using NLLO and NLLA calculations is alpha_S(MZ)=0.1189+-0.0008(stat.)+-0.0016(exp.)=-0.0010(had.)+-0.0036(theo.), with both measurements being in agreement with the world average.Comment: 4 pages, 2 figures, contribution to the Proceedings of Rencontres de Moriond, QCD Session, March 20th - 27th, 2011 in La Thuile, Italy; based on arXiv:1101.147