Sensitivity of Double Deeply Virtual Compton Scattering observables to Generalized Parton Distributions

TL;DR

This paper investigates how Double Deeply Virtual Compton Scattering (DDVCS) observables can reveal detailed information about proton structure through GPDs, highlighting its advantages over other processes and assessing experimental feasibility.

Contribution

It demonstrates the sensitivity of DDVCS asymmetries to proton GPDs and evaluates the potential for experimental measurements at major facilities.

Findings

DDVCS asymmetries are sensitive to GPDs across a broad phase space.

Feasibility of measuring GPDs at Jefferson Lab and Electron-Ion Collider is confirmed.

Unrestricted GPD extraction is possible due to the unique phase space of DDVCS.

Abstract

Double Deeply Virtual Compton Scattering (DDVCS) is a promising channel for Generalized Parton Distribution (GPD) studies as it is a generalization of the Deeply Virtual Compton Scattering (DVCS) and Timelike Compton Scattering (TCS) processes. Contrary to DVCS and TCS, the GPD phase space accessed through DDVCS is not constrained by on-shell conditions on the incoming and outgoing photons thus allowing unrestricted GPD extraction from experimental observables. Considering polarized electron and positron beams directed to a polarized proton target, we study the sensitivity of the DDVCS cross-section asymmetries to the chiral-even proton GPDs from different model predictions. The feasibility of such measurements is further investigated in the context of the CLAS and SoLID spectrometers at the Thomas Jefferson National Accelerator Facility and the future Electron-Ion Collider at the Brookhaven National Laboratory.