# A cascade of $e^-e^+$ pair production by a photon with subsequent annihilation to a single photon in a strong magnetic field

## TL;DR

This paper investigates a quantum electrodynamics process where a photon creates an electron-positron pair in a strong magnetic field, which then annihilates into a single photon, analyzing rates and polarization effects.

## Contribution

It provides the first calculation of the process amplitude and rate in low Landau levels, highlighting the dominance of resonant over nonresonant cases and detailing polarization characteristics.

## Key findings

- Resonant process rate exceeds nonresonant rate significantly.
- Final photon polarization is independent of initial polarization except for specific cases.
- Calculated process amplitude and rate in low Landau levels approximation.

## Abstract

The process of electron-positron pair production by a photon with subsequent annihilation to a single photon in a strong magnetic field has been studied. The general amplitude has been calculated and the process rate have been found in the low Landau levels approximation (resonant and nonresonant cases). The comparison of resonant and nonresonant cases shows a significant excess of the resonant rate. The polarization of the final photon in a strong magnetic field has also been found. It has been shown that polarizations of the initial and the final photons are independent except for the case of normal linear polarization of the initial photon.