Fast computing of final particle distributions in electron-laser scattering*

Near-future PetaWatt laser facilities will allow the exploration of uncharted regimes of Radiation Reaction and electron-positron pair production. One commonly proposed experimental configuration consists of a (near) head-on collision between a relativistic electron beam and an intense, short laser pulse. However, while the highest-intensity section of the laser generates the desired extreme conditions for the interaction, it is surrounded by lower-intensity regions that influence the overall experimental outcome. Moreover, micron-scale fluctuations in the synchronization of the collision can lead to significant changes in the features of the produced particles. Accurate modelling these setups is usually performed with full-scale QED particle-in-cell simulations. However, these require substantial computational resources, limiting parameter scans.

In this work, we have developed a fast, semi-analytical model that computes these asymptotic particle distributions. This framework can support efficient optimization and reconstruction of experimental parameters, particularly in the quest for specific Quantum Radiation Reaction and nonlinear Breit-Wheeler pair production signatures within electron distributions or emitted radiation.