Breit-Wheeler pair production in circularly polarized laser pulses seeded by a noble gas: Magnetic-field effects

We investigate the phenomenon of electron-positron pair production resulting from the interaction of neutral xenon gas with a high-intensity laser field. The pairs are generated through a combination of nonlinear Compton scattering and the Breit-Wheeler mechanism. We examine the pair-production process in a single circularly polarized laser pulse and in a combination of two counterpropagating pulses with opposite circular polarizations. Special focus is placed on analyzing the role of an additional external magnetic field. It is demonstrated that one can significantly enhance the positron yield by introducing a constant magnetic field, the strength of which is of the same order as the laser amplitude. We show that the magnetic field modifies the electron dynamics and gives rise to much larger values of the corresponding nonlinearity parameters for the particles. Within the framework of quantum electrodynamics, it is well known that these quantities predominantly govern the rates of photon emission and pair production; therefore, the magnetic field can considerably stimulate the mechanism of positron creation. In this context, we also discuss experimentally relevant scenarios where such strong magnetic fields may arise and prospects for determining laser intensity by measuring the number of positrons produced.