New physical processes for extracting GPDs with a better sensitivity to partonic structure

TL;DR

This paper proposes a new class of exclusive processes called SDHEPs to improve the measurement of generalized parton distributions, offering enhanced sensitivity to partonic structure and better discrimination of GPD types.

Contribution

It introduces SDHEPs as a novel approach for studying GPDs, with a two-stage framework and demonstrated potential at J-PARC, AMBER, and JLab.

Findings

SDHEPs provide increased sensitivity to GPD x-dependence.

Two specific processes are feasible for experimental measurement.

SDHEPs help disentangle different GPD types using spin asymmetries.

Abstract

We introduce a new type of exclusive processes for a better study of generalized parton distributions (GPDs), which we refer to as single-diffractive hard exclusive processes (SDHEPs). We advocate a two-stage framework for picturing SDHEPs based on the separation of scales, which gives a clear description both kinematically and dynamically. We examine the sensitivity of the SDHEP to the parton momentum fraction $x$-dependence of GPDs, and demonstrate it quantitatively with two specific processes that can be readily measured at J-PARC or AMBER using a pion beam and at JLab using a photon beam, respectively. Both processes are capable of providing enhanced sensitivity to the $x$-dependence, overcoming the problem of shadow GPDs, and disentangling different types of GPDs with various spin asymmetries.