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

TL;DR

This paper investigates the large-distance pion cloud contributions to nucleon parton densities in impact parameter space, linking chiral dynamics to flavor asymmetry in sea quarks and proposing a two-component nucleon structure model.

Contribution

It introduces a two-component nucleon model combining a core and a pion cloud, explaining sea quark flavor asymmetry through impact parameter analysis.

Findings

Large-distance pion cloud significantly contributes to sea quark asymmetry.

A two-component model explains the x-dependence of the asymmetry.

Universal large-distance region accounts for a substantial part of the asymmetry.

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 ~< M_pi/M_N and transverse distances b ~ 1/M_pi. 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 < b_core ~= 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.