Nucleon spin structure studies at Jefferson Lab

TL;DR

This paper discusses Jefferson Lab's measurements of nucleon spin structure at various Q^2 levels, shedding light on quark confinement, hadronic degrees of freedom, and advancing understanding of QCD and the strong force.

Contribution

It provides a comprehensive mapping of nucleon spin structure across different Q^2 ranges, enabling progress in theoretical models like Chiral Perturbation Theory and Light-Front Holographic QCD.

Findings

Enhanced understanding of quark confinement and hadronic degrees of freedom.

Improved determination of l_s at low energy.

Validation of theoretical models with experimental data.

Abstract

We report on the low and moderate Q^2 nucleon spin structure measurements done at Jefferson Lab, examining specifically the inclusive program. We discuss what the data teach us about quark confinement and the emergence of the effective hadronic degrees of freedom from the fundamental partonic ones. We show how this experimental program has reached its goal by providing a precise mapping at low, intermediate and moderately high Q^2 which has followed in many advances, e.g., with Chiral Perturbation Theory. Another example of a recent advance imputable to the JLab spin data is the improved understanding of \alpha_s at low energy, which allowed Light-Front Holographic QCD, an approximation to non-perturbative QCD, to derive the hadron spectrum from \Lambda_s.