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@ARTICLE{Smid:644993,
      author       = {Smid, Michal and Khademi, Pooyan and Ahmadiniaz, Naser and
                      Andrzejewski, Michal and Baehtz, Carsten and Brambrink, Erik
                      and Burian, Tomáš and Bulička, Jakub and Chalupský,
                      Jindřich and Cowan, Tom E. and Cafiso, Samuele Di Dio and
                      Chalupský, Jaromír and Cowan, Thomas E. and Göde,
                      Sebastian and Grenzer, Jörg and Hájková, Věra and Hilz,
                      Peter and Hippler, Willi and Höppner, Hauke and Horynová,
                      Alžběta and Huang, Lingen and Humphries, Oliver and
                      Jelínek, Šimon and Juha, Libor and Karbstein, Felix and
                      Kohlfürst, Christian and Garcia, Alejandro Laso and
                      Lötzsch, Robert and Matheron, Aimé and Masruri, Masruri
                      and Nakatsutsumi, Motoaki and Pelka, Alexander and Paulus,
                      Gerhard G. and Preston, Thomas R. and Randolph, Lisa and
                      Sävert, Alexander and Schlenvoigt, Hans-Peter and
                      Schützhold, Ralf and Schwinkendorf, Jan Patrick and
                      Stöhlker, Thomas and Toncian, Toma and Toncian, Monika and
                      Valialshchikov, Maxim and Rahul, Sripati V. and
                      Valialshchikov, Maksim and Vozda, Vojtěch and Weckert,
                      Edgar and Wessel, Colin and Wild, Jan and Zastrau, Ulf and
                      Zepf, Matt},
      title        = {{P}roof-of-principle experiment for the dark-field
                      detection concept for measuring vacuum birefringence},
      reportid     = {PUBDB-2026-00520, arXiv:2506.11649},
      year         = {2025},
      note         = {Phys.Rev.A 112 (2025) 6, 063512},
      abstract     = {Vacuum fluctuations give rise to effective nonlinear
                      interactions between electromagnetic fields. These
                      generically modify the characteristics of light traversing a
                      strong-field region. X-ray free-electron lasers (XFELs)
                      constitute a particularly promising probe, due to their
                      brilliance, the possibility of precise control and favorable
                      frequency scaling. However, the nonlinear vacuum response is
                      very small even when probing a tightly focused
                      high-intensity laser field with XFEL radiation and direct
                      measurement of light-by-light scattering of real photons and
                      the associated fundamental physics constants of the quantum
                      vacuum has not been possible to date. Achieving a
                      sufficiently good signal-to-background separation is key to
                      a successful quantum vacuum experiment. To master this
                      challenge, a dark-field detection concept has recently been
                      proposed. Here we present the results of a
                      proof-of-principle experiment validating this approach by
                      demonstrating that using real-world x-ray optics the
                      background signal can be suppressed sufficiently to measure
                      the weak nonlinear response of the vacuum.},
      cin          = {FS},
      ddc          = {530},
      cid          = {I:(DE-H253)FS-20120806},
      pnm          = {DFG project G:(GEPRIS)392856280 - FOR 2783: Probing the
                      Quantum Vacuum at the High-Intensity Frontier (392856280) /
                      DFG project G:(GEPRIS)416607684 - Vakuumdoppelbrechung
                      (416607684) / 631 - Matter – Dynamics, Mechanisms and
                      Control (POF4-631)},
      pid          = {G:(GEPRIS)392856280 / G:(GEPRIS)416607684 /
                      G:(DE-HGF)POF4-631},
      experiment   = {EXP:(DE-H253)XFEL-HED-20150101},
      typ          = {PUB:(DE-HGF)25},
      eprint       = {2506.11649},
      howpublished = {arXiv:2506.11649},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2506.11649;\%\%$},
      doi          = {10.3204/PUBDB-2026-00520},
      url          = {https://bib-pubdb1.desy.de/record/644993},
}