Strong-field Breit-Wheeler pair production with bremsstrahlung gamma-rays in the perturbative-to-nonperturbative transition regime

Photoproduction of electron-positron pairs by bremsstrahlung gamma-rays propagating through a high-intensity optical laser wave is studied. By calculating total pair production rates as well as energy and angular distributions of the produced particles for a range of laser intensities, we analyze the influence that the broad frequency spectrum of bremsstrahlung exerts on the properties of the process in the transition region between the perturbative and non-perturbative interaction regimes. In particular, we demonstrate a continuous shifting of the mainly contributing interval of bremsstrahlung frequencies during the course of the transition and indicate characteristic signatures of the laser-dressed particle mass.