Abstract
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function rather than with the usual parton density . This results in a nonintegrable singularity at exaggerated by the fact that ’s, on their own, have a singular Regge behavior for small . It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs that are finite and continuous at the “border point” . Using a simple input forward distribution, we illustrate implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the singularities is proposed that is based on the separation of the initial single DD into the “plus” part and the term. It is demonstrated that the “DD+D” separation method allows one to (re)derive GPD sum rules that relate the difference between the forward distribution and the border function with the -term function .
6 More- Received 26 January 2011
DOI:https://doi.org/10.1103/PhysRevD.83.076006
© 2011 American Physical Society