Generation of relativistic positrons carrying intrinsic orbital angular momentum

TL;DR

This paper introduces a theoretical framework for generating relativistic positrons with intrinsic orbital angular momentum (OAM) by using twisted photons, revealing how angular momentum is transferred during high-energy photon interactions.

Contribution

It develops a full-twisted scattering theory to describe angular momentum transfer, demonstrating how positrons can acquire OAM from twisted photons in high-energy processes.

Findings

Positrons can carry intrinsic OAM when produced by twisted photons.

The total angular momentum of photons is shared between the electron and positron.

Photon polarization significantly influences the OAM spectrum and scattering probability.

Abstract

High energy positrons can be efficiently created through high-energy photons splitting into electron-positron pairs under the influence of the Coulomb field. Here we show that a new degree of freedom-the intrinsic orbital angular momentum (OAM) can be introduced into relativistic positrons when the incident photons are twisted. We developed the full-twisted scattering theory to describe the transfer of angular momentum before and after the interaction. It is found that the total angular momentum (TAM) of the photon is equally distributed among the positron and electron. For each photon TAM value, the generated leptons gain higher average OAM number when the photon spin is anti-parallel to its TAM. The impact of photon polarization on the OAM spectrum profile and the scattering probability is more significant at small photon TAM numbers, owing to the various interaction channels influenced by flipping the photon spin. Our work provides the theoretical basis to study OAM physics in particle scattering and to obtain copious relativistic vortex positrons through the Beth-Heitler process.