Strong signature of one-loop self-energy in polarization resolved nonlinear Compton scattering

TL;DR

This paper demonstrates that one-loop self-energy radiative corrections significantly influence electron polarization in nonlinear Compton scattering, with potential for experimental observation using current laser technology.

Contribution

It introduces a method to isolate the non-radiative loop contribution to electron polarization in intense laser-electron interactions, highlighting its dominance in forward electron polarization.

Findings

Loop effect dominates forward electron polarization.

Polarization signal exceeds 10%, detectable experimentally.

Monte Carlo simulations confirm the theoretical predictions.

Abstract

The polarization dynamics of electrons including multiple nonlinear Compton scattering during the interaction of a circularly-polarized ultraintense laser pulse with a counterpropagating ultrarelativistic electron beam is investigated. While electron polarization emerges mostly due to spin-flips at photon emissions, there is a non-radiative contribution to the polarization which stems from the one-loop QED radiative corrections to the self-energy, which admits of a simple physical model. We put forward a method to single out the non-radiative contribution to the polarization, employing the reflection regime of the interaction when the radiation reaction is significant. The polarization of electrons that penetrate in the forward direction through a colliding laser is shown to be dominated by the loop effect, while the reflected electrons are mostly polarized by spin-flips at photon emissions. We confirm this effect by quantum Monte Carlo simulations considering the helicity transfer from the laser field to the electrons, taking into account the opposite sign of the polarizations induced by the non-radiative loop effect and radiative spin-flip. Our Monte Carlo simulations show a polarization signal as high as $\gtrsim 10\%$ from the non-radiative effect, amenable for experimental detection with current technology.