Nucleon Axial and Electromagnetic Form Factors

TL;DR

This paper calculates nucleon form factors using lattice QCD with multiple ensembles, controlling excited-state contamination, and analyzing the $Q^2$ behavior to determine charge radii and magnetic moments.

Contribution

It provides new lattice QCD results for nucleon form factors with improved control over excited states and systematic uncertainties.

Findings

Consistent nucleon form factors across multiple lattice ensembles.

Determined charge radii and magnetic moments with reduced systematic errors.

Analyzed $Q^2$ dependence using z-expansion and dipole models.

Abstract

We present results for the isovector axial, induced pseudoscalar, electric, and magnetic form factors of the nucleon. The calculations were done using $2+1+1$-flavor HISQ ensembles generated by the MILC collaboration with lattice spacings $a \approx$ 0.12, 0.09, 0.06$\mathrm{fm}$ and pion masses $M_\pi \approx$ 310, 220, 130$\mathrm{MeV}$. Excited-states contamination is controlled by using four-state fits to two-point correlators and by comparing two- versus three-states in three-point correlators. The $Q^2$ behavior is analyzed using the model independent z-expansion and the dipole ansatz. Final results for the charge radii and magnetic moment are obtained using a simultaneous fit in $M_\pi$, lattice spacing $a$ and finite volume.