NONPERTURBATIVE EXPANSION IN QCD

The purpose of this article is to construct the nonperturbative expans ion in quantum chromodynamics using a new small parameter and apply it to the investigation of the connection between nonperturbative and pe rturbative regimes of the effective coupling constant. We calculate th e nonperturbative renormalization group beta-function and discuss the properties of the series convergence using the two-loop approximation in this method. Based on the information from meson spectroscopy we de rive the effective coupling constant in the perturbative region.