Determination of ${\alpha }_S$ beyond $NNLO$ using the event shape averages

Abstract

In this proceedings we discuss a prescription to extract the QCD strong coupling constant at $N^{3}LO$ precision in perturbative QCD using a combination of $\mathcal{O}({\alpha }_S^3)$ calculations in pQCD and estimations of the $\mathcal{O}({\alpha }_S^4)$ corrections from the data. The method is applied to a set of event shape averages measured in experiments at the LEP, PETRA, PEP and TRISTAN colliders. In our analysis we account for hadronization effects with models from modern Monte Carlo event generators and analytic hadronization models. We conclude that the precision of the ${\alpha }_S$ extraction cannot be improved significantly only with pQCD predictions of higher orders, and further progress in these studies requires a significant advances in the studies and modeling of hadronization process.

Comments: Proceedings of 50th International Symposium on Multiparticle Dynamics