Pion cloud and sea quark flavor asymmetry in the impact parameter representation
Abstract
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, with a "core" antiquark distribution at b < bcore ~= 0.55 fm which vanishes at x -> 0 and the universal large-distance pion cloud, could naturally account for the x-dependence of the measured asymmetry.