Combining the small-x evolution and DGLAP for description of inclusive photon induced processes

Abstract

Abstract We study amplitudes of the inclusive photon induced high-energy processes: elastic Compton scattering off hadrons and photoproduction. Although description of these amplitudes includes both non-perturbative and perturbative contributions, QCD factorization makes possible to study them separately. Throughout the present paper we focus on the perturbative amplitudes and study such amplitudes in all available in the literature forms of QCD factorization: Collinear, $$K_T$$ KT and Basic. As a result, we obtain expressions for the perturbative Compton amplitudes, which can be used at arbitrary x and $$Q^2$$ Q2 in any form of QCD factorization. Putting $$Q^2 = 0$$ Q2=0 in those expressions allows us to obtain expressions for the perturbative components of the photoproduction amplitudes. The small-x asymptotics of the Compton amplitudes in any form of QCD factorization are of the Regge type, with the Reggeon being a double-logarithmic (non-BFKL) contribution to Pomeron.