Determination of the strong coupling constant\documentclass [12pt]{minimal}\usepackage {amsmath}\usepackage {wasysym}\usepackage {amsfonts}\usepackage {amssymb}\usepackage …

We present a determination of the strong coupling constant α s m Z using inclusive top-quark pair production cross section measurements performed at the LHC and at the Tevatron. Following a procedure first applied by the CMS Collaboration, we extract individual values of α s m Z from measurements by different experiments at several centre-of-mass energies, using QCD predictions complete in NNLO perturbation theory, supplemented with NNLL approximations to all orders, and suitable sets of parton distribution functions. The determinations are then combined using a likelihood-based approach, where special emphasis is put on a consistent treatment of theoretical uncertainties and of correlations between various sources of systematic uncertainties. Our final combined result is α s m Z= 0. 1177-0.0036+ 0.0034.