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



Aaboud, M, Aad, G, Abbott, B, Abdallah, J, Abdinov, O, Abeloos, B, Abidi, SH, AbouZeid, OS, Abraham, NL, Abramowicz, H
et al (show 2824 more authors) (2017) Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC NATURE PHYSICS, 13 (9). 852-+. ISSN 1745-2473, 1745-2481

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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 μ<sup>1</sup> 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<sup>(∗)</sup> + Pb<sup>(∗)</sup> <inf>γγ</inf>,for photon transverse energy E<inf>T</inf> > 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.

Item Type: Article
Additional Information: 34 pages in total, author list starting page 18, 6 figures, 2 tables. published version. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2016-05/
Uncontrolled Keywords: hep-ex, hep-ex, nucl-ex
Depositing User: Symplectic Admin
Date Deposited: 22 Sep 2017 15:26
Last Modified: 22 May 2026 19:39
DOI: 10.1038/NPHYS4208
Open Access URL: https://arxiv.org/abs/1702.01625
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3009588
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