We present the first determination of the strong coupling constant from the three-jet rate in e⁺e^- annihilation at LEP, based on a next-to-next-to-leading-order (NNLO) perturbative QCD prediction. More precisely, we extract αₛ(MZ) by fitting perturbative QCD predictions at O(αₛ³) to data from the ALEPH experiment at LEP. Over a large range of the jet-resolution parameter ycut, this observable is characterized by small nonperturbative corrections and an excellent stability under renormalization scale variation. We find αₛ(MZ)=0.1175±0.0020(expt)±0.0015(theor), which is more accurate than the values of αₛ(MZ) from e⁺e^- event-shape data currently used in the world average.
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Dissertori et al. (2010) studied this question.
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