The quantum chromodynamics (QCD) coupling ${\alpha }_s$ is not a physical observable of the theory, since it depends on conventions related to the renormalization procedure. We introduce a definition of the QCD coupling, denoted by ${\widehat{\alpha }}_s$, whose running is explicitly renormalization scheme invariant. The scheme dependence of the new coupling ${\widehat{\alpha }}_s$ is parametrized by a single parameter $C$, related to transformations of the QCD scale $\mathrm{\Lambda }$. It is demonstrated that appropriate choices of $C$ can lead to substantial improvements in the perturbative prediction of physical observables. As phenomenological applications, we study $e^{+}{e}^{-}$ scattering and decays of the $\tau$ lepton into hadrons, both being governed by the QCD Adler function.

• Received 27 June 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.152001