Vortex $\gamma$ photon generation via spin-to-orbital angular momentum transfer in nonlinear Compton scattering

TL;DR

This paper presents a quantum electrodynamics theory for generating vortex gamma photons through nonlinear Compton scattering, revealing how angular momentum transfer occurs and analyzing the properties of the emitted vortex photons.

Contribution

It introduces a detailed quantum electrodynamics framework for vortex gamma photon generation, including the vortex phase structure and the effects of finite laser pulses.

Findings

Vortex phase structure of the scattering matrix is unveiled.

The radiation rate of vortex gamma photons is derived.

Finite laser pulses influence the angular momentum and energy distribution.

Abstract

Vortex $\gamma$ photons with intrinsic orbital angular momenta (OAM) possess a wealth of applications in various fields, e.g.-strong-laser physics, nuclear physics, particle physics and astrophysics-yet their generation remains unsettled. In this work, we investigate the generation of vortex $\gamma$ photons via nonlinear Compton scattering of ultrarelativistic electrons in a circularly polarized laser pulse. We develop a quantum electrodynamics scattering theory that explicitly addresses the multiphoton absorption and the angular momentum transfer mechanism. In pulsed laser fields, we unveil the vortex phase structure of the scattering matrix element, discuss how the vortex phase could be transferred to the radiated photon, and derive the radiation rate of the vortex $\gamma$ photon. We numerically examine the energy spectra and beam characteristics of the radiation, while also investigating the influence of finite laser pulses on the angular momentum and energy distribution of the emitted vortex $\gamma$ photons.