Deeply virtual Compton scattering in the tensor-pomeron approach

Abstract

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 $Q^2\sim 20$ GeV${}^2$. 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 ${\gamma }^{\ast }p\to \gamma p$ as a function of $|t|$ and $Q^2$. The ratio $\tilde{R}(Q^2,W^2,t)=(d{\sigma }_{\mathrm{L}}/dt)/(d{\sigma }_{\mathrm{T}}/dt)$ 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.

20 pages, 7 figures

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Cited by in corpus (1)

• Central exclusive diffractive production of a single photon in high-energy proton-proton collisions within the tensor-Pomeron approach