Delbruck scattering in small scattering angle region

Abstract

The scattering of photons of x-ray energy off a Coulomb field in very forward scattering region may be thought as the refraction effect due to the Coulomb field. The cross section of the scattering can be computed from the photon bending angle obtained in geometrical optics. Its dependence on the fine structure constant is nonanalytic and softer than would the box diagrams of Delbruck scattering suggest. The refractive scattering is a nonlocal effect occurring over the distance scale of the impact parameter, and therefore may not be described by the single-box diagrams. We suggest that the scattering cross section is a consequence of the sum of the asymptotic series of the multi-box diagrams.