Dual parametrization of the proton generalized parton distribution functionsHandE, and description of the deeply virtual Compton scattering cross sections and asymmetries

Abstract

We develop the minimal model of a new leading order parameterization of GPDs introduced by Shuvaev and Polyakov. The model for GPDs H and E is formulated in terms of the forward quark distributions, the Gegenbauer moments of the D-term and the forward limit of the GPD E.The model is designed primarely for small and medium-size values of x B , x B ≤ 0.2. We examined two different models of the t-dependence of the GPDs: The factorized exponential model and the non-factorized Regge-motivated model. Using our model, we successfully described the DVCS cross section measured by H1 and ZEUS, the moments of the beam-spin A

Towards a fitting procedure for deeply virtual Compton scattering at next-to-leading order and beyond

“…We have also found in the expansion with respect to Legendre polynomials, which was used in Ref. [91], that the minimal version of the dual model, i.e., taking leading and next-to-leading partial waves, yields also an astonishing agreement with the exact result. We have also observed that in the experimentally accessible kinematical region the expansion in ξ practically coincides with the exact result, in particular for the imaginary part.…”

“…After crossing, cos θ becomes 16 the inverse of the scaling variable −η, i.e., cos θ = −1/η [24,90]. The basis of Legendre polynomials has later been adopted for the conformal moments of nucleon GPDs, too [91]. Let us here start with the analysis and discussion which basis of polynomials one should employ.…”

“…The DVCS data measured in fixed target [63,64] and collider [65,66,67] experiments have been confronted in the literature with theoretical predictions, e.g., color dipole model [168], collinear factorization approach within an aligned jet model inspired GPD ansatz [169] and the minimal dual GPD parameterization [91], see also Ref. [68] for a first analysis within the double distribution ansatz.…”

“…A partial wave expansion with respect to the angular momentum, the so-called dual GPD parameterization, has been proposed [90], where the partial wave amplitudes are those of the mesonic exchanges in the t-channel with given angular momentum. This also allows one to use the angular momentum as an expansion parameter [91] and Regge phenomenology as a guideline towards realistic GPD ansätze.…”

Generalized Parton Distributions at COMPASS

“…By the decomposition into Mellin moments it is straightforward to perform QCD evolution in this model. Calculations have been done by Guzey and Teckentrup [7]. Their dual parameterization with the Regge motivated t-dependence were used as model 3 in the simulations for COMPASS.…”