Nucleon structure from basis light-front quantization

TL;DR

This paper develops nucleon light-front wave functions using a basis approach, enabling calculation of form factors and parton distributions that largely agree with experimental data and lattice QCD, advancing understanding of nucleon structure.

Contribution

It introduces a basis light-front quantization method for nucleons, incorporating a confining potential and one-gluon exchange, to compute various nucleon properties.

Findings

Proton form factors match experimental data.

Valence quark PDFs are consistent with global fits.

Some neutron form factors and charge radius deviate from measurements.

Abstract

We produce the light-front wave functions (LFWFs) of the nucleon from a basis light-front ap- proach in the leading Fock sector representation. We solve for the mass eigenstates from a light-front effective Hamiltonian, which includes a confining potential adopted from light-front holography in the transverse direction, a longitudinal confinement, and a one-gluon exchange interaction with fixed coupling. We then employ the LFWFs to obtain the electromagnetic and axial form factors, the par- ton distribution functions (PDFs) and the generalized parton distribution functions for the nucleon. The electromagnetic and axial form factors of the proton agree with the experimental data, whereas the neutron form factors deviate somewhat from the experiments in the low momentum transfer region. The unpolarized, the helicity, and the transversity valence quark PDFs, after QCD scale evolution, are fairly consistent with the global fits to the data at the relevant experimental scales. The helicity asymmetry for the down quark also agrees well with the measurements, however, the asymmetry for the up quark shows a deviation from the data, especially in the small x region. We also find that the tensor charge agrees well with the extracted data and the lattice QCD predictions, while the axial charge is somewhat outside the experimental error bar. The electromagnetic radii of the proton, the magnetic radius of the neutron, and the axial radius are in excellent agreement with the measurements, while the neutron charge radius deviates from experiment.