Introduction

The strong coupling α_s is one of the fundamental parameters of the Standard Model (SM), setting the scale of the strength of the strong interaction theoretically described by Quantum Chromodynamics (QCD). Its measured (2014) value amounts to α_s(m²_Z) = 0.1185 ± 0.0006 at the reference Z pole mass scale. Given its current δα_s(m²_Z)/α_s(m²_Z) ≈ 0.5% uncertainty—orders of magnitude larger than that of the gravitational (δG/G ≈ 10−5), Fermi (δGF/GF ≈ 10−8), and QED (δα/α ≈ 10−10)couplings—the strong coupling is the least precisely known of all fundamental constants in nature.Improving our knowledge of αs is a prerequisite to reduce the theoretical uncertainties in the calculations of all high-precision perturbative QCD (pQCD) processes whose cross sections or decayrates depend on higher-order powers of αs, as is the case for virtually all those measured at the LHC. In the Higgs sector, in particular, the uncertainty on α_s is currently the second major contributor(after the bottom mass) to the parametric uncertainties of its dominant H → bb partial decay.The same applies for the extraction of the charm Yukawa coupling via future H → cc¯ measurements