Valence-quark structure N* resonances from DSEs

TL;DR

This paper compares two QCD-based models for nucleon and resonance form factors, demonstrating that a realistic momentum-dependent approach rectifies limitations of a simplified contact-interaction model, revealing key sensitivities in electromagnetic observables.

Contribution

It introduces a unified QCD-based framework for describing nucleon and resonance form factors and compares it with a contact-interaction model, highlighting the importance of momentum dependence.

Findings

Contact-interaction produces hard form factors and suppresses quark orbital correlations.

QCD-based approach rectifies defects of contact-interaction, providing more accurate form factors.

Certain observables are highly sensitive to the momentum dependence of QCD quantities.

Abstract

We present a unified Quantum Chromodynamics (QCD)-based description of elastic and transition electromagnetic form factors involving the nucleon and its resonances. We compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a confining, symmetry-preserving treatment of a vector$\,\otimes\,$vector contact-interaction in a widely-used leading-order (rainbow-ladder) truncation of QCD's Dyson-Schwinger equations. This comparison explains that the contact-interaction framework produces hard form factors, curtails some quark orbital angular momentum correlations within a baryon, and suppresses two-loop diagrams in the elastic and transition electromagnetic currents. Such defects are rectified in our QCD-based approach and, by contrasting the results obtained for the same observables in both theoretical schemes, shows those objects which are most sensitive to the momentum dependence of elementary quantities in QCD.