Review on alpha_s at LEP

Abstract

To measure the strong coupling alpha_s from event shape observables two ingredients are necessary. A perturbative prediction containing the dependence of observables on alpha_s and a description of the hadronisation process to match the perturbative prediction with the hadronic data. As perturbative prediction O(alpha_s^2), NLLA and combined calculations are available. Beside the well known Monte-Carlo based models also analytical predictions, so called power corrections, exist to describe the hadronisation. Advantages and disadvantages of the different resulting methods for determining the strong coupling and its energy dependence will be discussed, the newest DELPHI results will be presented, and an overview of the LEP results will be included.