Determination of the strong coupling constant $$\alpha _s \left( m_Z \right) $$ α s m Z from measurements of the total cross section for top–antitop-quark production

• Main Authors: Thomas Klijnsma, Siegfried Bethke, Günther Dissertori, Gavin P. Salam
• Format: Article
• Language: English
• Published: SpringerOpen 2017-11-01
• Series: European Physical Journal C: Particles and Fields
• Online Access: http://link.springer.com/article/10.1140/epjc/s10052-017-5340-5

Abstract We present a determination of the strong coupling constant $$\alpha _s \left( m_Z \right) $$ 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 $$\alpha _s \left( m_Z \right) $$ 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 $$\alpha _s \left( m_Z \right) =0.1177^{+0.0034{}}_{-0.0036{}}$$ α s m Z = 0 . 1177 - 0.0036 + 0.0034 .