학술논문

Deeply virtual Compton scattering off the neutron
Document Type
Article
Source
Nature Physics; February 2020, Vol. 16 Issue: 2 p191-198, 8p
Subject
Language
ISSN
17452473; 17452481
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 quasifree 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.