The spin content of the proton

TL;DR

This paper reviews recent advances in understanding the proton's spin structure, highlighting that polarized gluons contribute minimally and that quark and antiquark angular momentum account for most of the spin, explained through a relativistic, chirally symmetric model.

Contribution

It introduces a modern, relativistic, and chirally symmetric model that naturally explains the current experimental data on proton spin distribution.

Findings

Polarized gluons contribute very modestly to proton spin.

Most of the proton's spin is carried by confined quark and antiquark angular momentum.

The model explains current experimental limits on gluon polarization.

Abstract

Considerable progress has been made in our knowledge of the spin distribution within the proton. The recently measured limits on polarized gluons in the proton suggest polarized gluons contribute very modestly to the proton spin. We will show that a modern, relativistic and chirally symmetric description of the nucleon structure naturally explain the current proton spin data. Most of the "missing" spin is carried by confined quark and antiquarks' angular momentum.