Recent developments in nucleon spin structure with focus on h_{1L}^{\perp} and pretzelosity h_{1T}^\perp

TL;DR

This paper investigates the transverse momentum dependent parton distribution functions h_{1L}^{ot} and h_{1T}^ot (pretzelosity), exploring theoretical properties, testing approximations with experimental data, and making predictions for future measurements.

Contribution

It provides a detailed analysis of pretzelosity and h_{1L}^{ot}, tests the Wandzura-Wilczek-type approximation using HERMES data, and discusses relations between nucleon spin distributions in relativistic models.

Findings

The Wandzura-Wilczek approximation for h_{1L}^{ot} is practically useful based on HERMES data.

The difference between helicity and transversity distributions equals the transverse moment of pretzelosity in many models.

Preliminary deuteron data from COMPASS show asymmetries related to pretzelosity, supporting theoretical predictions.

Abstract

The leading twist transverse momentum dependent parton distribution functions h_{1L}^{\perp} and h_{1T}^\perp, which is sometimes called "pretzelosity," are studied. For h_{1L}^{\perp} we consider a "Wandzura-Wilczek-type" approximation, which follows from QCD equations of motion upon the neglect of pure twist-3 terms and allows to express it in terms of transversity. On the basis of available data from HERMES we test the practical usefulness of this approximation and discuss how it can be further tested by future CLAS and COMPASS data. We review the theoretical properties of retzelosity and observe an interesting relation valid in a large class of relativistic models: The difference between helicity and transversity distributions, which is often said to be a 'measure of relativistic effects' in the nucleon, is nothing but the transverse moment of pretzelosity. We discuss preliminary deuteron target data from COMPASS on the single spin asymmetry (SSA) in semi-inclusive deep inelastic scattering (SIDIS) related to pretzelosity, and make predictions for future experiments at JLab, COMPASS and HERMES.