Femto-Photography of Protons to Nuclei with Deeply Virtual Compton Scattering

Abstract

Developments in deeply virtual Compton scattering allow the direct measurements of scattering amplitudes for exchange of a highly virtual photon with fine spatial resolution. Real-space images of the target can be obtained from this information. Spatial resolution is determined by the momentum transfer rather than the wavelength of the detected photon. Quantum photographs of the proton, nuclei, and other elementary particles with resolution on the scale of a fraction of a femtometer is feasible with existing experimental technology.

Figures (2)

• Figure 1: Diagrammatic representation of the "handbag" diagram probed in DVCS; the crossed photon case is omitted. Emission of the final state photon from the target (solid $q'$ wave) and lepton beam (dashed $q'$ wave) with coherent interference is also shown. A Fourier transform ("FT") represented by a "lens" creates a probability map of the struck quark probability (shaded) on the transverse spatial image plane.
• Figure 2: Typical photos, or model images made from transverse position space ($\vec{b}_{T}$) amplitude squared; scale in Fermi. Images made on log-color plots. Left to right: Hofstadter's rendition; a model with transverse spin, plus a quadratic hole from 3-quark correlations; a proton one-half the size and more concentrated than traditional.