Super light-by-light scattering in vacuum induced by intense vortex lasers

TL;DR

This paper proposes a novel method to detect nonlinear vacuum polarization effects induced by intense vortex laser pulses, significantly improving signal strength and SNR, enabling single-shot detection with current laser and XFEL technologies.

Contribution

It introduces the super light-by-light scattering effect in vortex laser collisions, allowing direct VP signal detection without X-ray polarizers, and enhances detection efficiency.

Findings

Super-LBL produces signals with over 100 times higher SNR than previous methods.

The effect enables single-shot detection of nonlinear VP phenomena.

Signal photons are distinguished by large tangential momentum from the background.

Abstract

Collision of ultra-intense optical laser and X-ray free electron laser (XFEL) pulses is a promising approach to detecting nonlinear vacuum polarization (VP), a long-standing prediction of quantum electrodynamics remaining to be tested. Identifying the signals induced by polarized vacuum relies on purifying the X-ray polarization and poses significant challenges due to strongly reduced signal and low signal-to-noise ratio (SNR). Here we propose an approach that allows one to directly detect VP signals without the need for an X-ray polarizer. We identify a new VP effect in collision of an X-ray probe with an intense laser in a vortex mode, which we call the super light-by-light scattering (super-LBL), through which signal photons are kicked out of the X-ray background with large tangential momentum. Super-LBL originates from the gradient force of the vortical vacuum current in azimuthal direction and induces momentum exchange beyond the transverse momentum of laser-photon. This effect efficiently sets the scattered signal photons apart from the X-ray background, producing observable signals with both the strength and SNR more than two orders of magnitude higher than those from the known VP effects. This finding paves the way for single-shot detection of nonlinear VP phenomena with current ultra-intense laser and XFEL technologies.