Nonperturbative contributions to the quark form-factor at high-energy

Abstract

The analysis of nonperturbative effects in high energy asymptotics of the color singlet quark form factor is presented. We show that the nonperturbative effects determine the initial value for the perturbative evolution of the quark form factor and find their general structure with respect to the high energy asymptotics. Within the Wilson integral formalism which is natural for investigation of the soft, IR sensitive, part of the factorized form factor, we discuss the structure of the instanton induced effects in the evolution equation. It is demonstrated that the instanton contributions result in the finite renormalization of the subleading perturbative result and numerically are characterized by small factor reflecting the diluteness of the QCD vacuum within the instanton liquid model. The relevance of the IR renormalon induced effects in high energy asymptotic behavior is discussed. The consequences of the various analytization procedures of the strong coupling constant in the IR domain are considered.