Extracting generalized neutron parton distributions from 3He data

TL;DR

This paper analyzes the generalized parton distributions of 3He nucleus using impulse approximation, proposing a model-independent technique to extract neutron GPDs from experimental data, crucial for understanding neutron structure.

Contribution

It introduces a novel, model-independent method to extract neutron GPDs from 3He data, accounting for nuclear effects in the impulse approximation framework.

Findings

Neutron contribution dominates 3He GPDs at low momentum transfer.

Proposed extraction technique is independent of nuclear potential and nucleon model.

Coherent DVCS is promising for accessing neutron GPDs and parton orbital angular momentum.

Abstract

An impulse approximation analysis is described of the generalized parton distributions (GPDs) H and E of the 3He nucleus, quantities which are accessible in hard exclusive processes, such as coherent deeply virtual Compton scattering (DVCS). The calculation is based on the Av18 interaction. The electromagnetic form factors are correctly recovered in the proper limits. The sum of the GPDs H and E of 3He, at low momentum transfer, is largely dominated by the neutron contribution, thanks to the unique spin structure of 3He. This nucleus is therefore very promising for the extraction of the neutron information. By increasing the momentum transfer, however, this conclusion is somehow hindered by the the fast growing proton contribution. Besides, even when the neutron contribution to the GPDs of 3He is largely dominating, the procedure of extracting the neutron GPDs from it could be, in principle, nontrivial. A technique is therefore proposed, independent on both the nuclear potential and the nucleon model used in the calculation, able to take into account the nuclear effects included in the IA analysis and to safely extract the neutron information at values of the momentum transfer large enough to allow the measurements. Thanks to this observation, coherent DVCS should be considered a key experiment to access the neutron GPDs and, in turn, the orbital angular momentum of the partons in the neutron.