Bethe-Heitler pair production in ultrastrong short laser pulses

Production of electron-positron pairs from vacuum in the combined electromagnetic fields of a high-intensity laser pulse and an atomic nucleus is studied within the framework of laser-dressed quantum electrodynamics. The focus lies on the influence exerted by a finite laser pulse length on the energy spectra of created electrons and positrons, which is examined in a broad range of field frequencies and intensities. The results for an isolated short laser pulse are also compared with corresponding calculations for an infinite train of laser pulses. It is shown that the laser pulse length and its carrier-envelope phase have a substantial effect on the pair creation process, leading to both quantitative and qualitative differences in the particle spectra.