Measurement of the strong coupling alpha_S in e+e- annihilation using the three-jet rate

Abstract

We present a measurement of the strong coupling alpha_S using data collected with the JADE detector at centre-of-mass energies between 14 and 44 GeV. The three-jet rate as a function of the transition parameter ycut is determined using the Durham jet algorithm and the distribution is compared to QCD predictions. Recent theoretical calculations predict the three-jet rate at next-to-next-to-leading order. For the first time a measurement of alpha_S is presented using QCD predictions at next-to-next-to-leading order matched to predictions at next-to-leading logarithmic approximation, with subleading terms being included as well. We obtain alpha_S(Mz)=0.1199+-0.0010(stat.)+-0.0021(exp.)+-0.0054(had.)+-0.0007(theo.) being consistent with the world average value of alpha_S.Comment: 4 pages, 5 figures, Proceedings for the QCD July 2012 in Montpellie