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

M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B Abeloos, Sarah Abidi, O.S. AbouZeid, NL Abraham, H. Abramowicz, R. Abreu, H. Abreu, Y. Abulaiti, B.S. Acharya, Shin-ichi Adachi, L. Adamczyk, J P Adelman, Mogens Dam, Jørn Dines Hansen, Jørgen Beck HansenStefania Xella, Peter Henrik Hansen, Troels Christian Petersen, Ask Emil Løvschall-Jensen, Alejandro Alonso Diaz, James William Monk, Lars Egholm Pedersen, Graig Wiglesworth, Gorm Aske Gram Krohn Galster, Simon Holm Stark, Geert-Jan Besjes, Flavia de Almeida Dias, Fabian Alexander Jürgen Thiele, Milena Bajic, J. Barr

130 Citations (Scopus)
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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 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
JournalNature Physics
Volume13
Pages (from-to)852-858
ISSN1745-2473
DOIs
Publication statusPublished - 5 Sept 2017

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