One-photon pair-annihilation in pulsed plane-wave backgrounds

TL;DR

This paper investigates electron-positron pair annihilation into a single photon within pulsed plane-wave backgrounds, deriving probabilities, approximations, and analyzing the influence of initial states and particle distributions.

Contribution

It introduces a detailed calculation of the annihilation process in pulsed backgrounds, including a locally constant field approximation and Monte Carlo simulations, highlighting the impact of initial states.

Findings

Annihilation probability depends strongly on initial particle states.

Locally constant field approximation matches exact results well.

Initial wavepackets significantly influence the annihilation likelihood.

Abstract

We study the $2\rightarrow1$ process of electron-positron pair annihilation to a single photon in a plane-wave background. The probability of the process in a pulsed plane wave is presented, and a locally constant field approximation is derived and benchmarked against exact results. The stricter kinematics of annihilation (compared to the $1\rightarrow2$ processes usually studied) leads to a stronger dependence on the incoming particle states. We demonstrate this by studying the effect that initial state wavepackets have on the annihilation probability. The effect of annihilation in a distribution of particles is studied by incorporating the process into Monte Carlo simulations.