Locally monochromatic two-step nonlinear trident process in a plane wave

TL;DR

This paper investigates the two-step nonlinear trident process in plane waves at intermediate intensities, emphasizing the effects of photon polarisation and polarisation configurations on pair production rates using the locally monochromatic approximation.

Contribution

It introduces a detailed analysis of the nonlinear trident process with photon polarisation effects and compares different polarisation configurations, providing new insights into pair production mechanisms.

Findings

Photon polarisation decreases the trident rate by about 10%.

Polarisation effects are more significant at lower intensities.

Pair yield increases by approximately 30% with perpendicular polarised pulses.

Abstract

In many-cycle plane waves at intermediate intensities, the nonlinear trident process can be well-approximated by the two sequential steps of nonlinear Compton scattering of a polarised real photon followed by its transformation into an electron-positron pair via nonlinear Breit-Wheeler pair creation. We investigate this two-step process in the intermediate intensity regime by employing the locally monochromatic approximation for each step and numerically evaluating resulting expressions. When photon polarisation is included, it is found to produce an order 10% decrease in the trident rate: the importance of polarisation increases at lower intensities, and decreases at higher intensities. Its importance persists at higher intensities in a linearly-polarised background, but disappears at high intensities in a circularly-polarised background. If the two steps are made to take place in two linearly-polarised plane wave pulses with perpendicular polarisations, the pair yield can be increased by approximately 30% compared to two plane waves with the same polarisation. It is also shown that harmonic structures in the Compton step can be passed to the pair step if the Compton edge is at an energy of the order of the threshold for linear Breit-Wheeler.