Accepted Friday Nov 06, 2009
We study large-distance contributions to the nucleon's parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x b2 g, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/y production measured at HERA and FNAL. We show that our approach reproduces the general Nc-scaling of parton densities in QCD, thanks to the degeneracy of N and D intermediate states in the large-Nc limit. We also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.