Electromagnetic Form Factors of Hadrons in Quantum Field Theories

TL;DR

This paper compares two quantum field theories, Dual-$QCD_ ext{infty}$ and KLZ, to improve predictions of electromagnetic form factors of hadrons beyond naive VMD, showing excellent agreement with experimental data.

Contribution

It introduces and compares two QFT frameworks that enhance vector meson dominance predictions for hadron form factors.

Findings

Both theories significantly improve VMD predictions.

Results show excellent agreement with experimental data.

Perturbative expansion remains valid despite strong coupling.

Abstract

In this talk, recent results are presented of calculations of electromagnetic form factors of hadrons in the framework of two quantum field theories (QFT), (a) Dual-Large $N_c$ QCD (Dual-$QCD_\infty$) for the pion, proton, and $\Delta(1236)$, and (b) the Kroll-Lee-Zumino (KLZ) fully renormalizable Abelian QFT for the pion form factor. Both theories provide a QFT platform to improve on naive (tree-level) Vector Meson Dominance (VMD). Dual-$QCD_\infty$ provides a tree-level improvement by incorporating an infinite number of zero-width resonances, which can be subsequently shifted from the real axis to account for the time-like behaviour of the form factors. The renormalizable KLZ model provides a QFT improvement of VMD in the framework of perturbation theory. Due to the relative mildness of the $\rho\pi\pi$ coupling, and the size of loop suppression factors, the perturbative expansion is well defined in spite of this being a strong coupling theory. Both approaches lead to considerable improvements of VMD predictions for electromagnetic form factors, in excellent agreement with data.