ar X iv : h ep - p h / 02 09 01 6 v 1 2 S ep 2 00 2 1 The QCD Effective Charge to All Orders

Using the pinch technique, we show how to construct the QCD effective charge to all orders. The extension of the concept of the renormalization-group-invariant and process-independent effective charge from QED to QCD is of special interest for several reasons. First, the existence of a QED-like effective charge, and the ability to identify directly and unambiguously the infinite subset of gluon self-energy-like radiative corrections, is assumed in renormalon analysis of the behavior of the perturbative QCD series at high orders, and in particular, in the study of nonperturbative effects near the QCD mass scale [1]. Moreover, such an effective charge could serve as the natural scheme for defining the coupling in the recently proposed " event amplitude generator " based on the light-cone formulation of QCD [2]. Furthermore, when studying the interface between perturbative and non perturbative effects in QCD, one finds it advantageous to use this familiar QED concept, in conjunction with dispersive techniques and analicity properties of the S-matrix [3]. In QED, the effective charge construction proceeds as follows [4]: One begins by considering the unrenormalized photon self-energy Π