Quark-nucleon dynamics and deep virtual Compton scattering

Abstract

We consider deeply virtual Compton scattering and deep inelastic scattering in presence of Regge exchanges that are part of the non-perturbative quark-nucleon amplitude. In particular we discuss contribution from the Pomeron exchange and demonstrate how it leads to Regge scaling of the Compton amplitude. Comparison with HERA data is given.

Quark-nucleon dynamics and DVCS

“…Moreover, if data allow for interpretation without GPD's, one may question the physical content of all GPD models. We focus on applicability of the model [1,2,14] to DVCS in the HERA kinematics, Q 2 /W 2 << 1.…”

“…Six relevant Dirac-Lorentz structures that can appear in four fermion operators and conserve P, CP and CPT , as well as the quark helicity, are listed in Ref. [14] . Here, we concentrate on the Pomeron at Q 2 /W 2 1 that corresponds to HERA kinematics.…”

“…In order to obtain a finite contribution of the singlet GPD to the DVCS amplitude, it is necessary to abandon the collinear approximation in hard propagators [14]. This introduces a scale µ 2 associated with the parton-nculeon spectral function, which is absent in the scale-independent collinear approximation.…”

“…This scale dependence is of no surprise since Regge behavior does introduce a scale. In the limit Q 2 /µ 2 >> 1 it can be shown that the leading contribution of the Pomeron to the DVCS amplitude has the form [14] T DVCS ∼ Q 2α P −2 /x α P B ∼ W 2α P /Q 2 . This result was obtained in the limit Q 2 → ∞.…”