Generation of arbitrarily polarized GeV lepton beams via nonlinear Breit-Wheeler process

TL;DR

This paper proposes a method to generate highly polarized GeV lepton beams using nonlinear Breit-Wheeler pair production driven by high-energy polarized gamma photons and intense laser pulses, achieving up to 80% polarization.

Contribution

It introduces a fully spin-resolved semi-classical Monte Carlo model to predict polarization transfer in nonlinear Breit-Wheeler processes with asymmetric laser fields.

Findings

Dense GeV lepton beams with up to 80% polarization can be produced.

The polarization can be tuned between transverse and longitudinal components.

The method is feasible with current laser technology.

Abstract

Generation of arbitrarily spin-polarized lepton (here refer in particular to electron and positron) beams has been investigated in the single-shot interaction of high-energy polarized $\gamma$ photons with an ultraintense asymmetric laser pulse via nonlinear Breit-Wheeler (BW) pair production. We develop a fully spin-resolved semi-classical Monte Carlo method to describe the pair creation and polarization in the local constant field approximation. In nonlinear BW process the polarization of created pairs is simultaneously determined by the polarization of parent $\gamma$ photons, the polarization and asymmetry of scattering laser field, due to the spin angular momentum transfer and the asymmetric spin-dependent pair production probabilities, respectively. In considered all-optical method, dense GeV lepton beams with average polarization degree up to about $80\%$ (adjustable between the transverse and longitudinal components) can be obtained with currently achievable laser facilities, which could be used as injectors of the polarized $e^{+}e^{-}$ collider to search for new physics beyond the Standard Model.