Charge asymmetry in the differential cross section of high-energy e+e- photoproduction in the field of a heavy atom

TL;DR

This paper derives the first quasiclassical correction to the differential cross section of high-energy e+e- photoproduction in a heavy atom's electric field, revealing significant charge asymmetry effects especially at high transverse momenta.

Contribution

It provides the exact account of the electric field in the correction, highlighting the magnitude of charge asymmetry and estimating contributions from different diagrams.

Findings

Charge asymmetry can reach tens percent at high transverse momenta.

The correction is significant when transverse momenta are much larger than the electron mass.

Contribution from the Compton-type diagram is negligible for heavy nuclei.

Abstract

First quasiclassical correction to the differential cross section of high-energy electron-positron photoproduction in the electric field of a heavy atom is obtained with the exact account of the field. This correction is responsible for the charge asymmetry ${\cal A}$ in this process. When the transverse momentum of at least one of the produced particles is much larger than the electron mass $m$, the charge asymmetry can be as large as tens percent. We also estimate the contribution $\tilde{\cal A}$ to the charge asymmetry coming from the Compton-type diagram. For heavy nuclei, this contribution is negligible. For light nuclei, $\tilde{\cal A}$ is noticeable only when the angle between the momenta of electron and positron is of order of $m/\omega$ ($\omega$ is the photon energy) while the transverse momenta of both particles are much larger than $m$.