The dual parameterization of the proton generalized parton distribution functions H and E and description of the DVCS 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 \leq 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_{LU}^{\sin ϕ}, beam-charge A_{C}^{\cos ϕ} and transversely-polarized target A_{UT}^{\sin ϕ\cos ϕ} DVCS asymmetries measured by HERMES and A_{LU}^{\sin ϕ} measured by CLAS. The data on A_{C}^{\cos ϕ} prefers the Regge-motivated model of the t-dependence of the GPDs. The data on A_{UT}^{\sin ϕ\cos ϕ} indicates that the u and d quarks carry only a small fraction of the proton total angular momentum.