World Summary of αS (2012)

Determinations of the strong coupling strength, αS, are summarised and a new world average value of αS(MZ) is determined, using a new method of pre-averaging results within classes of measurements like hadronic τ decays, deep inelastic scattering processes, lattice calculations, electron-positron annihilation processes and electro-weak precision fits. The overall result isαS(MZ)=0.1184±0.0007, unchanged from the value obtained in 2009. This presentation is an excerpt from the QCD review section of the 2012 Review of Particle Physics (RPP) of the Particle Data Group [J. Beringer et al., Phys. Rev. D86 (2012) 010001; http://pdg.lbl.gov/.]. An earlier version of this work was also given in [S. Bethke, Nucl. Phys. Proc. Suppl. 222-224 (2012) 94-100.].