First determination of the strong coupling constant using NNLO predictions for hadronic event shapes in e+e− annihilations

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Published 13 February 2008 • Published under licence by IOP Publishing Ltd
, , Citation G. Dissertori et al JHEP02(2008)040 DOI 10.1088/1126-6708/2008/02/040

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Author affiliations

1 Institute for Particle Physics, ETH Zurich, 8093 Zurich, Switzerland

2 Institute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland

3 Institut für Theoretische Physik, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

4 Institute of Particle Physics Phenomenology, Department of Physics, University of Durham, Durham, DH1 3LE, U.K.

5 School of Physics, The University of Edinburgh, Edinburgh, EH9 3JZ, U.K.

6 II. Physikalisches Institut, Justus-Liebig Universität Giessen, Heinrich-Buff Ring 16, D-35392 Giessen, Germany

Dates

  1. Received 4 December 2007
  2. Accepted 1 February 2008
  3. Published

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1126-6708/2008/02/040

Abstract

We present the first determination of the strong coupling constant from a fit of next-to-next-to-leading order QCD predictions to event-shape variables, measured in e+e− annihilations at LEP. The data have been collected by the ALEPH detector at centre-of-mass energies between 91 and 206 GeV. Compared to results of next-to-leading order fits we observe that the central fit values are lower by about 10 %, with considerably reduced scatter among the results obtained with different event-shape variables. The dominant systematic uncertainty from renormalization scale variations is reduced by a factor of two. By combining the results for several event-shape variables and centre-of-mass energies, we find αs(M2Z) = 0.1240 ± 0.0008 (stat) ± 0.0010 (exp) ± 0.0011 (had) ± 0.0029 (theo).

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10.1088/1126-6708/2008/02/040