The QCD coupling $\alpha_s$ is extracted from the energy evolution of the first two moments (multiplicity and mean) of the parton-to-hadron fragmentation functions at low fractional hadron momentum $z$. Comparisons of the experimental $e^+e^-$ and deep-inelastic $e^\pm$p jet data to our NNLO$^*$+NNLL predictions, allow us to obtain $\alpha_s(m_{ _{ \rm Z}})$ = 0.1205$\pm$0.0010$^{ +0.0022}_{ -0.0000}$, in excellent agreement with the current world average determined using other methods at the same level of accuracy.
Categories: hep-ph hep-ex