Eur. Phys. J. C (2009) 59: 13-25
https://doi.org/10.1140/epjc/s10052-008-0836-7

Regular Article - Experimental Physics

Non-perturbative contribution to the thrust distribution in e⁺e⁻ annihilation

Cavendish Laboratory, J.J. Thomson Avenue, CB3 0HE, Cambridge, UK

^b webber@hep.phy.cam.ac.uk

Received: 26 September 2008
Revised: 17 November 2008
Published online: 12 December 2008

Abstract

We re-evaluate the non-perturbative contribution to the thrust distribution in e⁺e⁻→ hadrons, in the light of the latest experimental data and the recent NNLO perturbative calculation of this quantity. By extending the calculation to NNLO+NLL accuracy, we perform the most detailed study to date of the effects of non-perturbative physics on this observable. In particular, we investigate how well a model based on a low-scale QCD effective coupling can account for such effects. We find that the difference between the improved perturbative distribution and the experimental data is consistent with a 1/Q-dependent non-perturbative shift in the distribution, as predicted by the effective coupling model. Best fit values of α_s(91.2 GeV)=0.1164_−0.0026^+0.0028 and α₀(2 GeV)=0.59±0.03 are obtained with χ²/d.o.f.=1.09. This is consistent with NLO+NLL results but the quality of fit is improved. The agreement in α₀ is non-trivial because a part of the 1/Q-dependent contribution (the infrared renormalon) is included in the NNLO perturbative correction.