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

Research output: Contribution to journalArticlepeer-review

Authors

  • ATLAS Collaboration

Colleges, School and Institutes

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 μb−1 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 > 3 GeV, photon absolute pseudorapidity |η| < 2.4, diphoton invariant mass greater than 6 GeV, diphoton transverse momentum lower than 2 GeV 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.

Bibliographic note

31 pages in total, author list starting page 15, 3 figures, 2 tables. Submitted to Nature Physics. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2016-05/

Details

Original languageEnglish
Pages (from-to)852–858
Number of pages7
JournalNature Physics
Volume13
Issue number9
Publication statusPublished - 14 Aug 2017

Keywords

  • hep-ex, nucl-ex