title: Precise determination of the strong coupling constant at NNLO in QCD from the three-jet rate in electron-positron annihilation at LEP.
abstract: 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 alpha{s}(M{Z}) by fitting perturbative QCD predictions at O(alpha{s}{3}) to data from the ALEPH experiment at LEP. Over a large range of the jet-resolution parameter y{cut}, this observable is characterized by small nonperturbative corrections and an excellent stability under renormalization scale variation. We find alpha{s}(M{Z})=0.1175+/-0.0020(expt)+/-0.0015(theor), which is more accurate than the values of alpha{s}(M{Z}) from e{+}e{-} event-shape data currently used in the world average.
authors.affiliation: Institute for Particle Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Dissertori
authors.forename: A
authors.initials: A
authors.lastname: Gehrmann-Deridder
authors.forename: T
authors.initials: T
authors.lastname: Gehrmann
authors.forename: E W N
authors.initials: EW
authors.lastname: Glover
authors.forename: G
authors.initials: G
authors.lastname: Heinrich
authors.forename: H
authors.initials: H
authors.lastname: Stenzel