Spectral caustics in laser assisted Breit-Wheeler process

TL;DR

This paper investigates electron-positron pair production in a strong laser field, revealing spectral caustics in the transverse momentum spectrum that can be predicted using stationary phase analysis, with practical experimental setups discussed.

Contribution

It introduces the concept of spectral caustics in the Breit-Wheeler process within laser pulses and demonstrates their theoretical prediction and potential experimental observation.

Findings

Identification of caustic peaks in the momentum spectrum

Analytical method using stationary phases to locate caustics

Feasibility of observing effects with current XFEL facilities

Abstract

Electron-positron pair production by the Breit-Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering.