Variational perturbation theory and analytic properties of the running expansion parameter of QCD

Abstract

Analytic properties of the nonperturbative running expansion pa­rameter in quantum chromodynamics which is appeared within vari­ational perturbation theory are investigated. We argue that a re­quirement of the Kallen-Lehmann analyticity allows one to define a variational parameter the value of which is agreed well with non­perturbative data coming from the meson spectroscopy.