On the observability of field-assisted birefringent Delbrück scattering

Abstract

We consider the scattering of an x-ray free-electron laser (XFEL) beam on the superposition of a strong magnetic field Bext with the Coulomb field Eext of a nucleus with charge number Z. In contrast to pure Delbrück scattering (Coulomb field only), the magnetic field Bext introduces an asymmetry (i.e., polarization dependence) and renders the effective interaction volume quite large, while the nuclear Coulomb field facilitates a significant momentum transfer ∆k. For a field strength of Bext = 10 6 T (corresponding to an intensity of order 10 22 W/cm 2 ) and an XFEL frequency of 24 keV, we find a differential cross section dσ/dΩ ∼ 10 −25 Z 2 /(∆k) 2 in forward direction for one nucleus. Thus, this effect might be observable in the near future at facilities such as the Helmholtz International Beamline for Extreme Fields (HIBEF) at the European XFEL.

Quantum vacuum signatures in multi-color laser pulse collisions

“…We are confident that the concepts outlined and applied in the present study will prove very useful in future attempts at optimizing photonic signatures of quantum vacuum nonlinearity for given experimental parameters and constraints. Our formalism can also provide for an efficient basis to study recent alternative suggestions [57,58] for corresponding discovery experiments beyond the optical regime.…”

X-ray vacuum diffraction at finite spatio-temporal offset

“…X-ray vacuum diffraction is generic to probe photons of arbitrary polarization. Besides, it provides an additional means to improve the signal-to-background separation [17][18][19][20][21] in high-intensity laser driven vacuum birefringence experiments [22][23][24][25][26][27][28][29][30]. Vacuum birefringence is already actively searched for in experiments employing continuous wave lasers in combination with high-finesse cavities as probe and macroscopic magnetic fields of a few Tesla to induce the effect [31][32][33].…”