paper

Dual parametrization of GPDs versus the double distribution Ansatz

arXiv:0811.2901 · doi:10.1140/epja/i2008-10759-2

Abstract

We establish a link between the dual parametrization of GPDs and a popular parametrization based on the double distribution Ansatz, which is in prevalent use in phenomenological applications. We compute several first forward-like functions that express the double distribution Ansatz for GPDs in the framework of the dual parametrization and show that these forward-like functions make the dominant contribution into the GPD quintessence function. We also argue that the forward-like functions with contribute to the leading singular small- behavior of the imaginary part of DVCS amplitude. This makes the small- behavior of $\im A^{DVCS}$ independent of the asymptotic behavior of PDFs. Assuming analyticity of Mellin moments of GPDs in the Mellin space we are able to fix the value of the -form factor in terms of the GPD quintessence function and the forward-like function .

18 pages, 5 figures. A version that appeared in Eur. Phys. J. A. Some of the statements were refined and misprints in the formulas were corrected

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