Delbruck scattering in small scattering angle region

TL;DR

This paper investigates x-ray photon scattering at small angles in a Coulomb field, proposing a refractive interpretation and analyzing the nonlocal effects and multi-box diagram contributions to the scattering cross section.

Contribution

It introduces a refractive perspective on Delbruck scattering at small angles and suggests the cross section results from the sum of multi-box diagrams, highlighting nonlocal effects.

Findings

Scattering cross section depends on the fine structure constant in a nonanalytic way.

Refractive scattering occurs over the impact parameter scale, not describable by single-box diagrams.

Multi-box diagrams contribute significantly to the scattering process.

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.