Achievements and open issues in the determination of polarized parton distribution functions

TL;DR

This paper reviews the current status of polarized parton distribution functions, highlighting recent experimental achievements such as evidence of polarized sea quark asymmetry and positive polarized gluon distribution, and discusses open issues and future prospects.

Contribution

It provides a comprehensive analysis of experimental data in perturbative QCD, emphasizing recent advances from polarized proton-proton collision measurements and identifying key open questions.

Findings

Evidence of sizable polarized light sea quark asymmetry

Detection of a positive polarized gluon distribution in the proton

Discussion of open issues and future experimental directions

Abstract

I review the current status of the determination of helicity-dependent, or polarized, parton distribution functions from a comprehensive analysis of experimental data in perturbative quantum chromodynamics. I illustrate the latest achievements driven by new measurements in polarized proton-proton collisions at the Relativistic Heavy Ion Collider, namely the first evidence of a sizable polarized light sea quark asymmetry and of a positive polarized gluon distribution in the proton. I discuss which are the open issues in the determination of polarized distributions, and how these may be addressed in the future by ongoing, planned and proposed experimental programs.