# Multi-photon regime of non-linear Breit-Wheeler and Compton processes in short linearly and circularly polarized laser pulses

## TL;DR

This paper investigates non-linear Breit-Wheeler and Compton processes in short polarized laser pulses, revealing how multi-photon contributions and pulse polarization affect angular distributions, with implications for carrier envelope phase measurement.

## Contribution

It provides a detailed analysis of multi-photon effects and polarization dependence in non-linear pair production and Compton scattering in short laser pulses, including CEP influence.

## Key findings

- Multi-photon processes significantly contribute to total cross sections.
- Azimuthal distributions differ qualitatively between linear and circular polarization.
- CEP causes non-monotonic behavior in angular distributions, useful for CEP determination.

## Abstract

Non-linear Breit-Wheeler $e^+e^-$ pair production and its crossing channel - the non-linear Compton process - in the multi-photon regime are analyzed for linearly and circularly polarized short laser pulses. The contribution of multi-photon processes to total cross sections is determined and we also show that (i) the azimuthal angular distributions of outgoing electrons in these processes differ on a qualitative level, and (ii) they depend on the polarization properties of the pulses. A finite carrier envelope phase (CEP) leads to a non-trivial non-monotonic behavior of the azimuthal angle distributions of the considered processes. That effect can be used for the CEP determination.