Leading Nucleon Form Factors in Single Gauge Boson Exchange Approximation

TL;DR

This paper calculates leading nucleon form factors at high momentum transfer using QCD and distribution amplitudes, comparing results with experimental data and previous theoretical approaches.

Contribution

It provides a complete calculation of nucleon form factors in the single gauge boson exchange approximation combining QCD perturbation theory with nucleon distribution amplitudes.

Findings

Results agree with experimental data using third order polynomials for distribution amplitudes.

Identifies and discusses a discrepancy in the Dirac form factor of the proton compared to previous results.

Proposes an explanation for the symmetry factor discrepancy in existing theoretical models.

Abstract

We provide a complete calculation of all leading nucleon form factors at large momentum transfer and in single gauge boson exchange approximation. In order to evaluate the required nucleon transition probability matrix elements, we combine QCD perturbation theory with an expansion in nucleon distribution amplitudes. Using leading twist nucleon distribution amplitudes only, one obtains the desired nucleon form factors. The obtained results are consistent with experimental data when we use third order polynomials for the distribution amplitudes and non-perturbative models for the coefficients. Finally, we compare our results for the Dirac form factor of the proton with previous results based on the QCD factorization theorem, where a discrepancy about the correct symmetry factor is still under discussion. We examine the calculations and propose an explanation.