Pion cloud and sea quark flavor asymmetry in the impact parameter representation

We study large-distance contributions to the nucleon 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 ∼< Mpi/ MN and transverse distances b ∼ 1/Mpi. We analyze the phenomenological ''pion cloud'' model of the flavor asymmetry dbar(x) - ubar(x) and quantify what fraction of the calculated asymmetry results from the universal large-distance region. Our findings indicate that a two-component picture of the nucleon's partonic structure -- a ''core'' antiquark distribution at b < bcore ∼ 0.55 fm which vanishes at x -> 0, and the universal large-distance pion cloud at b > bcore -- could naturally account for the x-dependence of the measured asymmetry.