High-energy $e^+e^-$ photoproduction in the field of a heavy atom accompanied by bremsstrahlung

TL;DR

This paper derives exact helicity amplitudes and differential cross sections for high-energy electron-positron photoproduction with bremsstrahlung in a heavy atom's electric field, highlighting Coulomb corrections' significant impact.

Contribution

It provides the first exact derivation of helicity amplitudes and cross sections in the leading quasiclassical approximation for this process, including Coulomb corrections.

Findings

Coulomb corrections significantly modify the differential cross section.

Coulomb corrections induce azimuthal asymmetry for circularly polarized initial photons.

Results are valid for high-energy, small-angle scattering in the field of a heavy atom.

Abstract

Helicity amplitudes and differential cross section of high-energy $e^+e^-$ photoproduction accompanied by bremsstrahlung in the electric field of a heavy atom are derived. The results are exact in the nuclear charge number and obtained in the leading quasiclassical approximation. They correspond to the leading high-energy small-angle asymptotics of the amplitude. It is shown that, in general, the Coulomb corrections essentially modify the differential cross section as compared to the Born result. When the initial photon is circularly polarized the Coulomb corrections lead to the asymmetry in the distribution over the azimuth angles $\varphi_i$ of produced particles with respect to the replacement $\varphi_i\to -\varphi_i$.