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

Abstract : Light-by-light scattering ($\gamma\gamma\rightarrow\gamma\gamma$) 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 (Pb) ions. Using 480 $\mu$b$^{-1}$ of Pb+Pb collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, the ATLAS Collaboration reports evidence for the $\gamma\gamma\rightarrow\gamma\gamma$ reaction. A total of 13 candidate events are observed with an expected background of 2.6$\pm$0.7 events. After background subtraction and analysis corrections, the fiducial cross section of the process $\textrm{Pb+Pb}\,(\gamma\gamma)\rightarrow \textrm{Pb}^{(\ast)}\textrm{+}\textrm{Pb}^{(\ast)}\,\gamma\gamma$, for photon transverse energy $E_{\mathrm{T}}>$3 GeV, photon absolute pseudorapidity $|\eta|<$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 $\pm$ 24 (stat.) $\pm$ 17 (syst.) nb, which is in agreement with Standard Model predictions.
Type de document :
Article dans une revue
Nature Physics, Nature Publishing Group, 2017, 13, pp.852-858. 〈https://www.nature.com/nphys/journal/v13/n9/full/nphys4208.html〉. 〈10.1038/nphys4208〉
Domaine :

http://hal.in2p3.fr/in2p3-01458929
Contributeur : Claudine Bombar <>
Soumis le : mardi 7 février 2017 - 10:01:24
Dernière modification le : lundi 9 avril 2018 - 12:22:11

### Citation

M. Aaboud, N. Berger, A.M. Burger, M. Delmastro, L. Di Ciaccio, et al.. Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC. Nature Physics, Nature Publishing Group, 2017, 13, pp.852-858. 〈https://www.nature.com/nphys/journal/v13/n9/full/nphys4208.html〉. 〈10.1038/nphys4208〉. 〈in2p3-01458929〉

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