Deeply virtual Compton scattering in the tensor-pomeron approach

The two-tensor-pomeron model proposed previously to describe low x DIS data is applied to real and virtual Compton scattering on a proton. The model includes two tensor pomerons, a soft and a hard one, and tensor reggeons. We include contributions of both transverse and longitudinal virtual photons. We show that this model gives a very good description of experimental data at small Bjorken x on deeply virtual Compton scattering (DVCS) from HERA. The reggeon exchange term is particularly relevant for describing the real-photon-proton scattering measured at lower gamma p energies at FNAL. We present two fits which differ somewhat in the strength of the hard pomeron contribution. In both fits we find that the interference between soft- and hard-pomeron exchange plays an important role. We find that in DVCS the soft-pomeron contribution is considerable up to Q(2) similar to 20 GeV2. Our model allows to study the transition from the small-Q(2) regime, including the photoproduction (Q(2) = 0) limit, to the large-Q(2) regime, the DIS limit. We also discuss the ratio of cross sections for longitudinally and transversely polarized virtual photons in gamma* p -> gamma p as a function of vertical bar t vertical bar and Q(2). The ratio (R) over tilde (Q(2) , W-2, t) = (d sigma(L)/dt)/(d sigma(T)/dt) strongly increases with t. Our findings may be checked in future lepton-nucleon scattering experiments in the low-x regime, for instance, at a future Electron-Ion Collider at the BNL (EIC), and, if LHeC is realized, at the LHC. (C) 2022 The Author(s). Published by Elsevier B.V.