Deeply virtual Compton scattering off the neutron

TL;DR

This paper reports the first measurement of deeply virtual Compton scattering off a neutron, providing new insights into the neutron's internal quark structure and contributing to the understanding of nucleon structure and the proton spin puzzle.

Contribution

It presents the first observation and analysis of unpolarized DVCS off a neutron using a deuterium target, extracting neutron-specific Compton form factors.

Findings

Extracted neutron cross-sections from deuterium data

Determined quark flavor contributions to nucleon structure

Enhanced understanding of nucleon internal dynamics

Abstract

The three-dimensional structure of nucleons (protons and neutrons) is embedded in so-called generalized parton distributions, which are accessible from deeply virtual Compton scattering. In this process, a high energy electron is scattered off a nucleon by exchanging a virtual photon. Then, a highly-energetic real photon is emitted from one of the quarks inside the nucleon, which carries information on the quark's transverse position and longitudinal momentum. By measuring the cross-section of deeply virtual Compton scattering, Compton form factors related to the generalized parton distributions can be extracted. Here, we report the observation of unpolarized deeply virtual Compton scattering off a deuterium target. From the measured photon-electroproduction cross-sections, we have extracted the cross-section of a quasi-free neutron and a coherent deuteron. Due to the approximate isospin symmetry of quantum chromodynamics, we can determine the contributions from the different quark flavours to the helicity-conserved Compton form factors by combining our measurements with previous ones probing the proton's internal structure. These results advance our understanding of the description of the nucleon structure, which is important to solve the proton spin puzzle.