Non-Perturbative Contribution to the Thrust Distribution in $e^+ e^-$ Annihilation

R. A. Davison; B. R. Webber

Paper

Non-Perturbative Contribution to the Thrust Distribution in $e^+ e^-$ Annihilation

Abstract

We re-evaluate the non-perturbative contribution to the thrust distribution in

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

-dependent non-perturbative shift in the distribution, as predicted by the effective coupling model. Best fit values of

and

are obtained with

. This is consistent with NLO+NLL results but the quality of fit is improved. The agreement in

is non-trivial because a part of the 1/Q-dependent contribution (the infrared renormalon) is included in the NNLO perturbative correction.