Two-component model for the axial form factor of the nucleon

TL;DR

This paper introduces a two-component model for the nucleon’s axial form factor, combining quark structure and meson cloud effects, and predicts a zero in the form factor between 2 and 3 GeV$^2$, differing from traditional dipole models.

Contribution

The study presents a novel two-component model that accurately fits experimental data and predicts a zero in the form factor, providing new insights into nucleon structure.

Findings

Model reproduces experimental data with minimal parameters.

Predicts a zero in the form factor between 2 and 3 GeV$^2$.

Provides the first theoretical extrapolation to the time-like region.

Abstract

The axial form factor of the nucleon is studied in a two-component model consisting of a three-quark intrinsic structure surrounded by a meson cloud. The experimental data in the space-like region are well reproduced with a minimal number of parameters. The results are similar to those obtained from a dipole fit up to 1 GeV$^2$, but they surprisingly show a zero between 2 and 3 GeV$^2$. Such behavior, predicted by the present model completely disagrees with the dipole parametrization. The theoretical expression for the form factor is then analytically extrapolated to the time-like region, giving the first predictions in this regime. This kinematical region is especially interesting for present and future colliders.