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

Abstract

The experiment on laser light backscattering on relativistic electrons was carried out at the VEPP-2000 collider. Laser radiation (λ0 10.6 µm) 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.

Observation of a fine structure in e+e− → hadrons production at the nucleon-antinucleon threshold

“…energy spread. The beam energy and energy spread have been monitored by the back-scattering-laser-light system [23,24], providing an absolute energy measurement with better than 0.1 MeV uncertainty in every single measurement. During data taking the E c.m.…”

A system of beam energy measurement based on the Compton backscattered laser photons for the VEPP-2000 electron–positron collider

“…The layout of the beam energy measurement system is shown in Fig.3. In this case the energy spectrum of scattered photons (Fig.2) is described by the formulae [11]:…”

Study of the process e+e− → K+K−η with the CMD-3 detector at the VEPP-2000 collider

“…The integrated luminosity at each energy point was deter-mined using events of the processes e + e − →e + e − and e + e − →2γ [17]. The beam energy was monitored by measuring the current in the dipole magnets of the main ring (in 2011 and 2012), and by using the Back-Scattering-Laser-Light system (in 2017) [18,19]. In the runs of 2011 and 2012 we use the measured average momentum of electrons and positrons in events of Bhabha scattering, as well as the average momentum of proton-antiproton pairs from the process e + e − →pp process [20] to determine the actual E c.m.…”