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Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC

  • ATLAS Collaboration
  • iThemba Labs
  • Department of Physics
  • University of South Africa
  • Cadi Ayyad University
  • Moroccan Foundation for Advanced Science Innovation and Research (MAScIR)
  • Dep Física and CEFITEC of Faculdade de Ciências e Tecnologia
  • NOVA University Lisbon
  • CERN
  • Mohamed I University
  • Aix-Marseille Université
  • University of Oklahoma
  • University of Texas at Arlington
  • Azerbaijan National Academy of Sciences
  • IN2P3/CNRS
  • University of Toronto
  • University of California at Santa Cruz
  • University of Sussex
  • Tel Aviv University
  • Technion-Israel Institute of Technology
  • University of Oregon
  • Stockholm University
  • Oskar Klein Centre
  • National Institute for Nuclear Physics
  • Abdus Salam International Centre for Theoretical Physics
  • The University of Tokyo
  • AGH University of Krakow
  • Northern Illinois University
  • Ludwig Maximilian University of Munich
  • Rutherford Appleton Laboratory
  • University of Belgrade
  • Alexandru Ioan Cuza University of Iaşi
  • Laboratório de Instrumentação e Física Experimental de Partículas
  • University of Granada
  • Boston University
  • Joint Institute for Nuclear Research
  • University of Rome Tor Vergata
  • Kyoto University
  • Lund University
  • P.N. Lebedev Physical Institute of the Russian Academy of Sciences
  • University of Bologna
  • University of Victoria BC
  • Universidad Nacional de La Plata
  • Horia Hulubei National Institute of Physics and Nuclear Engineering
  • National Technical University of Athens
  • Czech Technical University in Prague
  • University of Salento
  • The University of Chicago

Research output: Contribution to journalArticlepeer-review

350 Scopus citations

Abstract

Light-by-light scattering (γγ → γγ) is a quantum-mechanical process that is forbidden in the classical theory of electrodynamics. This reaction is accessible at the Large Hadron Collider thanks to the large electromagnetic field strengths generated by ultra-relativistic colliding lead ions. Using 480 μ1 of lead-lead collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, here we report evidence for light-by-light scattering. A total of 13 candidate events were observed with an expected background of 2.6 ± 0.7 events. After background subtraction and analysis corrections, the fiducial cross-section of the process Pb + Pb (γγ) → Pb(∗) + Pb(∗) γγ,for photon transverse energy ET > 3GeV, photon absolute pseudorapidity |η| <2.4, diphoton invariant mass greater than 6GeV, diphoton transverse momentum lower than 2GeV and diphoton acoplanarity below 0.01, is measured to be 70 ± 24 (stat.) ±17 (syst.) nb, which is in agreement with the standard model predictions.

Original languageEnglish
Pages (from-to)852-858
Number of pages7
JournalNature Physics
Volume13
Issue number9
DOIs
StatePublished - Sep 5 2017

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