Rho zero electroproduction and the hadronic contribution to deeply virtual compton scattering

Abstract

A two-gluon-exchange model incorporating perturbative and non-perturbative effects is presented for ρ electroproduction which provides an excellent description of all current data. This is then used to calculate the contribution from the ρ to deeply virtual Compton scattering via the vector-meson-dominance transition ρ → γ. This is found to be sufficiently large to provide a significant contribution through interference with the perturbative QCD term.

Colour dipoles and virtual Compton scattering

“…that z, d T and the quark helicities, which are left implicit in the above equation, remain unchanged in diffractive † For further discussion of this approximation, see [22] and the original paper [21].…”

Unified model of exclusiveρ0,φ, andJ/ψelectroproduction

“…This model is based on our earlier work [5], which modelled ρ electroproduction by "open pair" production in the region of the ρ mass. In particular, a successful description of the data was obtained by combining the nonperturbative amplitude of section 3.1 with the perturbative amplitude of section 3.2.1, using an empirical slope parameter to describe the t-dependence of the latter.…”

“…The approach has the advantage of providing a common kinematical structure in which it is possible to separate the part of the vector-meson production amplitude describing the kinematics from the part which describes the dynamics of the process [5]. This separation then allows the nonpertubative and perturbative contributions to be combined at the amplitude level.…”

“…In a previous paper [5] we have successfully applied this approach to calculate ρ electroproduction in a model which avoids the vertex function complication, following [13], by considering open qq-pair production with the invariant mass of the qq pair restricted to the region of the ρ mass. However this method cannot be applied to higher-mass vector mesons: for a qq with an invariant mass in the region of the ρ there are no states available except the ρ itself (making a 10% allowance for ω production), but this is not true for the φ and J/ψ.…”

Quark-nucleon dynamics and deep virtual Compton scattering

“…tions can be well fitted in terms of simple functions of Q 2 and the center of mass energy, W rather then Q 2 and x B [31][32][33].…”