Determination of $

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_s16-0.0008(stat.)_s16-0.0013(exp.)_s16-0.0010(had.)_s16-0.0024(theo.) and the result using NLLO and NLLA calculations is alpha_S(MZ)=0.1189_s16-0.0008(stat.)_s16-0.0016(exp.)=-0.0010(had.)_s16-0.0036(theo.), with both measurements being in agreement with the world average.