Nucleon Charge and Magnetization Densities in the Perturbative Chiral Quark Model

Abstract

This study investigates the distributions of charge and magnetization within the nucleon using the Perturbative Chiral Quark Model (PCQM). Nucleon charge and magnetization densities are intrinsically linked to the Sachs electromagnetic form factors. We calculated these Sachs form factors within the PCQM framework, incorporating excited-state quark propagators up to the 2^nd excited state. Our findings reveal that both the influence of the meson cloud surrounding the quarks within the nucleon and the inclusion of excited-state quark propagators contribute significantly to the Sachs form factors. The definitions of the nucleon charge and magnetization densities are dependent on the chosen frame of reference. Accordingly, we calculated these densities in both the rest frame and the infinite momentum frame of the nucleon. Our results demonstrate distribution patterns consistent with those reported in previous studies. Specifically, the neutron spherical charge density in the rest frame is observed to be positive near the center and at large distances, with a negative distribution in the intermediate region. Conversely, in the infinite momentum frame, the neutron charge distribution exhibits a negative core surrounded by a positive region extending away from the center.