New approach to QCD Factorization
Ioffe Physical Technical Institute (St Peterburg)
Mercredi 26/11/2014, 14:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
Factorization is the fundamental concept in order to apply QCD calculations to description of hadronic reactions. According to Factorization, theoretical study of any hadronic process includes both parton scattering and parton distributions. The partonic sub-processes are calculated with the use of regular methods of perturbative QCD. In contrast, theparton distributions are introduced purely phenomenologically, without any theoretical grounds. There are two popular kinds of Factorization in the literature: collinear and kT factorizations. They were introduced independently of each other. We show that both the kT and collinear factorization can be obtained by consecutive reductions of some more general (Basic) factorization. Each of these reductions is an approximation valid under certain assumptions. par First, the transitions from Basic to kT factorization assumes that the momenta of the partons connecting the perturbative and non-perturbative blobs are mostly transverse. This assumption fairly agrees both with the DGLAP and BFKL. par Second, if the unintegrated parton distributions in kT factorization have a maximum(s) in kT , then kT factorization can be reduced to collinear factorization. The sharper the maximum is, the better is accuracy of the transition. par This assumption can be checked with analysis of available experimental data. Integration over momenta of the connecting partons in the Basic factorization for amplitudes of the forward Compton scattering off hadrons must yield a finite result. This obvious requirement allowed us to deduce theoretical constraints on the parton distributions both in kT and Collinear factorizations.