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SUMMARY:Dark-field Concept for the Measurement of Weak Quantum Vacuum Sign
 als
DTSTART:20260528T140000Z
DTEND:20260528T150000Z
DTSTAMP:20260605T205100Z
UID:indico-event-405@indico.xfel.eu
DESCRIPTION:Speakers: Felix Karbstein (Helmholtz Institute Jena and Instit
 ute of Theoretical Physics\, University of Jena\, Jena\, Germany)\n\nMode
 rn physics views the vacuum not as the absence of everything\, but as a hi
 ghly non-trivial quantum state characterized by the omnipresence of vacuum
  fluctuations. It encodes information about the full particle content of t
 he underlying microscopic theory in the form of virtual processes. Because
  electromagnetic fields couple to charges\, vacuum fluctuations of charged
  particles are predicted to give rise to nonlinear self-couplings of elect
 romagnetic fields. These couplings inherently modify Maxwell’s linear th
 eory of classical electrodynamics and — at least in principle — invali
 date the superposition principle. At the same time\, for the field strengt
 hs reached by macroscopic electromagnetic fields currently available in th
 e laboratory the quantum vacuum nonlinearities induced by Standard Model p
 articles are very small\, with the leading correction governed by quantum 
 electrodynamics (QED). For these reasons\, this fundamental tenet\, antici
 pated 90 years ago in the seminal theoretical work of Heisenberg and Euler
  [1]\, has remained experimentally challenging and is yet to be tested in 
 the laboratory.\nBecause of their brilliance and a favorable frequency sca
 ling X-ray free-electron lasers (XFELs) constitute a particularly promisin
 g probe. However\, the effect is very small even when probing a tightly fo
 cused high-intensity laser field with XFEL radiation. Achieving a sufficie
 ntly good signal-to-background separation is key to its first successful d
 etection in a controlled laboratory experiment. To master this challenge\,
  several years ago we have proposed a dark-field detection concept [2] tha
 t was later successfully validated in a proof-of-principle experiment at t
 he HED/HIBEF instrument of the European XFEL [3]. In this talk\, I will in
 troduce and explain the dark-field concept\, provide predictions for the a
 ttainable signals and discuss the status and perspectives of this approach
  for the measurement of light-by-light scattering signals in a dedicated e
 xperiment within the BIREF@HIBEF Collaboration [4].\n[1] W. Heisenberg\, H
 . Euler\, Z. Physik 98\,714–732 (1936)\n[2] F. Karbstein\, D. Ullmann\, 
 E. A. Mosman\, M. Zepf\, Phys. Rev. Lett. 129(6)\, 061802 (2022)\n[3] M. 
 Šmíd\, et al\, Phys. Rev. A 112 (6)\, 063512 (2025)\n[4] N. Ahmadiniaz\,
  et al.\, High Power Laser Science and Engineering 13\, e7 (2025)\n \nVir
 tual participation (via Zoom):\nhttps://xfel.zoom.us/j/63148539246?pwd=gEX
 X0wUiRNKi49KlvLDqcISVn8O311.1\nMeeting ID: 631 4853 9246\nPasscode: 874304
 \n\nhttps://indico.xfel.eu/event/405/
LOCATION:XHV / Auditorium (European XFEL)
URL:https://indico.xfel.eu/event/405/
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