Backscattering of Laser Radiation on Ultra-Relativistic Electrons in Transverse Magnetic Field: Evidence of Photon Interference in a MeV Scale

TL;DR

This study experimentally investigates laser light backscattering on ultra-relativistic electrons in a magnetic field, revealing photon interference effects that deviate from classical predictions, consistent with historical QED forecasts.

Contribution

First experimental evidence of photon interference in laser backscattering on ultra-relativistic electrons within a magnetic field, confirming long-standing QED predictions.

Findings

Energy spectrum differs from Klein-Nishina cross section due to magnetic field effects

Experimental data aligns with classical electrodynamics explanations

Supports QED predictions made over 40 years ago

Abstract

The experiment on laser light backscattering on relativistic electrons was carried out at the VEPP-2000 collider. Laser radiation ({\lambda}0 10.6 {\mu}m) was scattered head-on the 990 MeV electrons inside the dipole magnet, where an electron orbit radius is about 140 cm. The energies of backscattered photons were measured by the HPGe detector. It was observed experimentally that due to the presence of magnetic field, energy spectrum of backscattered photons differs from the Klein-Nishina cross section. The explanation of the effect is proposed in terms of classical electrodynamics. Moreover, it appears that the exact QED predictions for the phenomenon were done more than 40 years ago.