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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 is αₛ (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.
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S. Bethke (2012) studied this question.