Parton distribution functions and quark orbital motion

TL;DR

This paper investigates how the covariant quark-parton model reveals the significant impact of quark orbital motion on structure functions, especially in polarized cases, and proposes a method to extract polarized quark distributions.

Contribution

It introduces a covariant framework highlighting the role of quark orbital momentum and provides a new procedure to derive polarized quark distributions from structure functions.

Findings

Quark orbital motion significantly affects polarized structure functions.

The covariant model links intrinsic quark motion to observable structure functions.

A method to extract polarized quark distributions from experimental data is proposed.

Abstract

Covariant version of the quark-parton model is studied. Dependence of the structure functions and parton distributions on the 3D quark intrinsic motion is discussed. The important role of the quark orbital momentum, which is a particular case of intrinsic motion, appears as a direct consequence of the covariant description. Effect of orbital motion is substantial especially for polarized structure functions. At the same time, the procedure for obtaining the quark momentum distributions of polarized quarks from the combination of polarized and unpolarized structure functions is suggested.