Theory Group Seminars

New appoach to QCD factorization

by Boris Ermolaev (Ioffe Physical Technical Institute, San Pietroburgo, Russia)

248 (Building C, First floor)


Building C, First floor

Abstract: Factorization is a fundamental concept suggested in order to apply QCD calculations to description of hadronic reactions. According to this concept, a theoretical study of any hadronic process should combine perturbative calculations (to calculate partonic sub-processes) with parton distributions (to proceed from the partons to hadrons). The partonic sub-processes are calculated with the use of regular techniques developed in perturbative QCD (either at fixed orders in the coupling or by using Evolution Equations). In contrast, the parton distributions are introduced purely phenomenologically without any theoretical grounds. There are two kinds of QCD factorizations available in the literature: i) collinear factorization, and ii) K_T-factorization, introduced independently of each other. Considering the structure functions of Deep-Inelastic Scattering, we show that both K_T- and collinear factorizations can be obtained by consecutive reductions of a more general factorization which we call "basic factorization". As an application of our results, we obtain theoretical restrictions on fits for the parton distributions. First, we predict a general form of fits for parton distributions in K_T-factorization. Second, we exclude the use of singular factors x^{-a} (with a > 0) in fits for the initial quark and gluon distributions in both K_T- and collinear factorizations.