Twist-three distributions and their appearance in the doubly-polarized Drell-Yan process

TL;DR

This paper explores twist-three quark distributions in polarized hadrons, deriving sum rules and analyzing their influence on the double-spin asymmetry in Drell-Yan processes.

Contribution

It introduces a detailed analysis of twist-three distributions, deriving sum rules and clarifying their role in polarized Drell-Yan asymmetries.

Findings

Derivation of sum rules for $g_2$ and $h_2$

Explanation of their role in $A_{LT}$ asymmetry

Connection between quark-gluon operators and measurable quantities

Abstract

The twist-three distributions $g_2(x)$ and $h_2(x)$ are defined as quark-field matrix elements between polarized hadron states. They can be written in terms of quark-mass and gluonic operators, after which the Burkhardt-Cottingham sum rule for $g_2$ can be derived and a similar sum rule for $h_2$. Their role in the Drell-Yan double-spin asymmetry $A_{LT}$ is explained.