# Revisiting model relations between T-odd transverse-momentum dependent parton distributions and generalized parton distributions

## TL;DR

This paper examines the theoretical connection between generalized parton distributions and T-odd effects in single spin asymmetries, highlighting the specific conditions under which such relations hold, mainly in simplified hadron models.

## Contribution

It clarifies the conditions necessary for establishing relations between GPDs and T-odd effects, emphasizing model-dependent constraints and providing examples of applicable models.

## Key findings

- Relations are only valid under specific model conditions.
- Nontrivial relations require helicity-conserving couplings.
- Applicable models include scalar-diquark and quark-target models.

## Abstract

We revisit the connection between generalized parton distributions in impact parameter space and T-odd effects in single spin asymmetries of the semi-inclusive deep inelastic process. We show that nontrivial relations can be established only under very specific conditions, typically realized only in models that describe hadrons as two-body bound systems and involving a helicity-conserving coupling between the gauge boson and the spectator system. Examples of these models are the the scalar-diquark spectator model or the quark-target model for the nucleon, and relativistic models for the pion at the lowest order in the Fock-space expansion.