Nonlinear Breit-Wheeler pair production in collisions of bremsstrahlung γ quanta and a tightly focused laser pulse

Experimental efforts toward the detection of the nonperturbative strong-field regime of the BreitWheeler pair creation process plan to combine incoherent sources of GeV ?? quanta and the coherent fields of tightly focused optical laser pulses. This endeavor 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 focusing 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.