QCD Perturbation Theory at Low Energies

Abstract

We apply the optimization procedure based on the Principle of Minimal Sensitivity to the third-order calculation of $\mathbb{R}$. The effective couplant remains finite, freezing to a value ${\alpha }_s/\pi =0.26$ at low energies. Using Poggio-Quinn-Weinberg smearing we find good agreement between theory and experiment right down to zero energy.

Comments: 11 pages including 3 Postscript Figures using Epsf.tex, LaTex