The $g_2$ Structure Function

TL;DR

This paper explores the physical interpretation of the polarized structure function g_2, its moments, and their relation to quark-gluon correlations, transverse forces, and generalized parton distributions in nucleons.

Contribution

It provides a novel interpretation of the x^2 moment of g_2 and e(x) as measures of transverse forces on quarks, linking structure functions to internal nucleon dynamics.

Findings

x^2 moment of g_2 relates to average transverse force on quarks

Connections established between g_2 moments and generalized parton distributions

Insights into quark transversity dependence of transverse forces

Abstract

Polarized structure functions at low $Q^2$ have the physical interpretation of (generalized) spin polarizabilities. At high $Q^2$, the polarized parton distribution $g_2(x)$ provides access to quark-gluon correlations in the nucleon. We discuss the interpretation of the $x^2$ moment of $\bar{g}_2(x)$ as an average transverse force on quarks in deep-inelastic scattering from a transversely polarized target. Qualitative connections with generalized parton distributions are emphasized. The $x^2$ moment of the chirally-odd twist-3 parton distribution $e(x)$ provides information on the dependence of the average transverse force on the transversity of the quark.