Determination of the Strong Coupling Beyond NNLO Using Event Shape Averages

We present a method of extracting the strong coupling at (NLO)-L-3 precision in QCD using a combination of O(alpha(3)(S)) perturbative calculations with estimations of the O(alpha(4)(S)) corrections from data. We apply the procedure to a set of event shape averages measured at the LEP, PETRA, PEP, and TRISTAN colliders. We account for non-perturbative effects using both modern Monte Carlo event generators as well as analytic models. Our results show that the precision of alpha(S) extraction cannot be significantly improved solely with higher-order perturbative QCD predictions, but requires also a significant refinement of the understanding and modeling of the hadronization process.