Hadron optics: Diffraction patterns in deeply virtual Compton scattering

We show that the Fourier transform of the deeply virtual Compton scattering (DVCS) amplitude with respect to the skewness variable at fixed invariant momentum transfer squared t provides a unique way to visualize the structure of the target hadron in the boost-invariant longitudinal coordinate space. The results are analogous to the diffractive scattering of a wave in optics. As a specific example, we utilize the quantum fluctuations of a fermion state at one loop in QED to obtain the behavior of the DVCS amplitude for electron-photon scattering. We then simulate the wavefunctions for a hadron by differentiating the above LFWFs with respect to M-2 and study the corresponding DVCS amplitudes in light-front longitudinal space. In both cases we observe that the diffractive patterns in the longitudinal variable conjugate to sharpen and the positions of the first minima move in with increasing momentum transfer. For fixed I, higher minima appear at positions which are integral multiples of the lowest minimum. Both these observations strongly support the analogy with diffraction in optics. (c) 2006 Elsevier B.V. All rights reserved.