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@ARTICLE{Aad:646429,
      author       = {Aad, Georges and others},
      collaboration = {{ATLAS Collaboration}},
      title        = {{O}bservation of $t\bar{t}\gamma\gamma$ production at
                      $\sqrt{s}=$13 {T}e{V} with the {ATLAS} detector},
      journal      = {Physics letters / B},
      volume       = {874},
      issn         = {0031-9163},
      address      = {Amsterdam},
      publisher    = {North-Holland Publ.},
      reportid     = {PUBDB-2026-00850, arXiv:2506.05018. CERN-EP-2025-125.
                      arXiv:2506.05018. CERN-EP-2025-125},
      pages        = {19},
      year         = {2026},
      note         = {37 pages in total, author list starting page 20, 3 figures,
                      1 table, submitted to Phys. Lett. B. All figures including
                      auxiliary figures are available at
                      https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2023-03},
      abstract     = {This paper presents the first observation of top-quark pair
                      production in association with two photons
                      ($t\bar{t}\gamma\gamma$). The measurement is performed in
                      the single-lepton decay channel using proton-proton
                      collision data collected by the ATLAS detector at the Large
                      Hadron Collider. The data correspond to an integrated
                      luminosity of 140 fb$^{-1}$ recorded during Run 2 at a
                      centre-of-mass energy of 13 TeV. The $t\bar{t}\gamma\gamma$
                      production cross section, measured in a fiducial phase space
                      based on particle-level kinematic criteria for the lepton,
                      photons, and jets, is found to be $2.42^{+0.58}_{-0.53}\,
                      \text{fb}$, corresponding to an observed significance of 5.2
                      standard deviations. Additionally, the ratio of the
                      production cross section of $t\bar{t}\gamma\gamma$ to
                      top-quark pair production in association with one photon is
                      determined, yielding $(3.30^{+0.70}_{-0.65})\times
                      10^{-3}$.},
      cin          = {ATLAS},
      ddc          = {530},
      cid          = {I:(DE-H253)ATLAS-20120731},
      pnm          = {611 - Fundamental Particles and Forces (POF4-611) / DFG
                      project G:(GEPRIS)469666862 - Präzisionstests des
                      Standardmodells unter der Verwendung von geboosteten
                      W/Z-Bosonen am Large Hadron Collider (469666862) / DITTO -
                      Comprehensive search for new phenomena in the dilepton
                      spectrum at the LHC (101089007) / REALDARK - REAL-time
                      discovery strategies for DARK matter and dark sector signals
                      at the ATLAS detector with Run-3 LHC data (101002463) / BARD
                      - B-resonance Algorithm using Rare Decays (101116429)},
      pid          = {G:(DE-HGF)POF4-611 / G:(GEPRIS)469666862 /
                      G:(EU-Grant)101089007 / G:(EU-Grant)101002463 /
                      G:(EU-Grant)101116429},
      experiment   = {EXP:(DE-H253)LHC-Exp-ATLAS-20150101},
      typ          = {PUB:(DE-HGF)16},
      eprint       = {2506.05018},
      howpublished = {arXiv:2506.05018},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2506.05018;\%\%$},
      url          = {https://bib-pubdb1.desy.de/record/646429},
}