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

We present a measurement of the strong coupling αS 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 αS 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 αS(MZ0)=0.1199±0.0010(stat.)±0.0021(exp.)±0.0054(had.)±0.0007(theo.), being consistent with the world average value of αS.