Proton spin in a light-cone chiral quark model

TL;DR

This paper investigates the proton's spin structure using a light-cone chiral quark model, emphasizing the effects of quark transverse motion and Melosh-Wigner rotation, and successfully reproduces experimental polarized structure functions.

Contribution

It introduces a light-cone formalism approach to the chiral quark model, incorporating Melosh-Wigner rotation effects to better match experimental data on proton spin structure.

Findings

Results align well with experimental data on $g_1(x)$

Inclusion of Melosh-Wigner rotation improves model accuracy

Provides detailed $x$-dependence of polarized quark distributions

Abstract

We discuss the spin structure of the proton in a light-cone treatment of the chiral quark model. Based on the fact that the quark helicity ($\Delta q$) measured in polarized deep inelastic scattering experiments is actually the quark spin defined in the light-cone formalism, rather than the quark spin ($\Delta q_{QM}$) defined in the conventionally quark model (or in the rest frame of the nucleon), we calculate the $x$-dependence of the polarized quark distribution functions $\Delta q(x)$, and the polarized structure functions $g_1 (x)$. Special attention is focused on the Melosh-Wigner rotation due to the transversal motions of quarks inside the nucleon and its effects on the bare quark input. It is shown that our results match the experimental data well.