# Re-examining valence quark spin distributions

## TL;DR

This paper re-evaluates how hyperfine interactions and the pion cloud break SU(6) symmetry, affecting valence quark spin distributions in the proton, and compares these effects with experimental data in the intermediate x region.

## Contribution

It provides a detailed analysis of two mechanisms breaking SU(6) symmetry and their impact on spin-dependent valence quark distributions, tested against experimental data.

## Key findings

- Both mechanisms can explain the observed spin asymmetries.
- The effects are significant in the region 0.3 < x < 0.7.
- The mechanisms are consistent with known data.

## Abstract

The observed deep inelastic nucleon spin asymmetries $A_{1}^{p,n}$ and the spin dependent quark distributions break SU(6) spin - flavour symmetry. In quark models two mechanisms for breaking SU(6) symmetry are well known: the hyperfine interaction and the pion cloud of the nucleon. I re-evaluate these mechanisms and show how the breaking of SU(6) in each case affects spin dependent valence quark distributions of the proton. In particular I investigate the properties of these mechanisms in the kinematic region $0.3 < x < 0.7$ and attempt to test these against known data. Both mechanisms are able to explain the quantitative features of the spin asymmetries.