Non-linear Breit-Wheeler pair production in collisions of bremsstrahlung $\gamma-$quanta and a tightly focussed laser pulse

TL;DR

This paper models how the shape and focusing of laser pulses influence the production of electron-positron pairs when high-energy gamma rays from bremsstrahlung collide with intense laser fields, aiding experimental design.

Contribution

It provides detailed estimates of pair yields considering laser focusing effects and compares these with plane-wave models, optimizing laser parameters for maximum pair production.

Findings

Focusing geometry significantly affects pair yield.

Gaussian pulse envelopes enhance pair production.

Optimized laser parameters increase pair yield at fixed energy.

Abstract

Experimental efforts toward the detection of the nonperturbative strong-field regime of the Breit-Wheeler pair creation process plan to combine incoherent sources of GeV $\gamma$ quanta and the coherent fields of tightly focussed optical laser pulses. This endeavour calls for a theoretical understanding of how the pair yields depend on the applied laser field profile. We provide estimates for the number of produced pairs in a setup where the high-energy radiation is generated via bremsstrahlung. Attention is paid to the role of the transversal and longitudinal focussing of the laser field, along with the incorporation of a Gaussian pulse envelope. We compare our corresponding results with predictions from plane-wave models and determine the parameters of focused laser pulses which maximize the pair yield at fixed pulse energy. Besides, the impact of various super-Gaussian profiles for the laser pulse envelope and its transverse shape is discussed.