# The GPD H-tilde and spin correlations in wide-angle Compton scattering

## TL;DR

This paper analyzes wide-angle Compton scattering using the handbag approach, focusing on form factors and GPDs, and discusses how future measurements can improve understanding of spin correlations and GPDs.

## Contribution

It highlights the current limitations in knowledge of certain GPDs and form factors, and proposes using future spin correlation data to better constrain these quantities.

## Key findings

- Form factor R_A and GPD H-tilde are poorly known.
- Future spin correlation measurements can help extract R_A.
- Constraints on the large -t behavior of H-tilde can be improved.

## Abstract

Wide-angle Compton scattering (WACS) is discussed within the handbag approach in which the amplitudes are given by products of hard subprocess amplitudes and form factors, specific to Compton scattering, which represent 1/x-moments of generalized parton distributions (GPDs). The quality of our present knowledge of these form factors and of the underlying GPDs is examined. As will be discussed in some detail the form factor R_A and the underlying GPD H-tilde are poorly known. It is argued that future data on the spin correlations A_{LL} and/or K_{LL} will allow for an extraction of R_A which can be used to constrain the large -t behavior of H-tilde.