Pulse envelope effects in nonlinear Breit-Wheeler pair creation

The effect of the pulse envelope on electron-positron pair creation in a circularly polarized laser pulse is investigated. Interference on the length scale of the pulse envelope, and smoothness of the pulse edges are found to influence the pair spectrum. A toy model of a flat-top pulse is used to identify pulse envelope effects inaccessible to local approaches. Broadening of channel openings and a widening of the energy and transverse momentum distribution of the pair are found to receive contributions that are below the local harmonic threshold. By comparing pair yields in a flat-top, sine-squared and Gaussian pulse, a link between pulse shape and photon-polarized Breit-Wheeler pair creation is found. In the transverse momentum distribution, a signal of pulse envelope interference is found in an azimuthal asymmetry, which appears in intense fields and persists in long pulses.

Automated summary

The effect of the pulse envelope on electron-positron pair creation in a circularly polarized laser pulse is investigated, with interference and smoothness influencing the pair spectrum. By comparing pair yields in different pulse shapes, a link between pulse shape and photon-polarized Breit-Wheeler pair creation is found. In the transverse momentum distribution, a signal of pulse envelope interference is discovered, showing azimuthal asymmetry in intense fields and long pulses.