Nonlinear Breit-Wheeler pair production in a tightly focused laser beam

TL;DR

This paper develops an analytical framework to study nonlinear Breit-Wheeler pair production in realistic, tightly focused laser beams with complex space-time structures, revealing significant differences from idealized plane wave models.

Contribution

It introduces a new analytical approach for strong-field QED processes in arbitrary laser beam geometries, extending beyond the plane wave approximation.

Findings

Significant quantitative differences in positron spectra compared to plane wave models.

Framework applicable to realistic laser beam configurations.

Results relevant for upcoming high-intensity laser experiments.

Abstract

The only available analytical framework for investigating QED processes in a strong laser field systematically relies on approximating the latter as a plane wave. However, realistic high-intensity laser beams feature much more complex space-time structures than plane waves. Here, we show the feasibility of an analytical framework for investigating strong-field QED processes in laser beams of arbitrary space-time structure by determining the energy spectrum of positrons produced via nonlinear Breit-Wheeler pair production as a function of the background field in the realistic assumption that the energy of the incoming photon is the largest dynamical energy in the problem. A numerical evaluation of the angular resolved positron spectrum shows significant quantitative differences with respect to the analogous result in a plane wave, such that the present results will be also important for the design of upcoming strong laser facilities aiming at measuring this process.