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

Abraham, N L, Allbrooke, B M M, Asquith, L, Cerri, A, Chavez Barajas, C, DeSanto, A, Jones, S D, Lerner, G, Miano, F, Salvatore, F, Santoyo Castillo, I, Shaw, K, Stevenson, T, Suruliz, K, Sutton, M, Tresoldi, F, Trovato, F, Vivarelli, I, Winkels, E, Winston, O J, The ATLAS Collaboration, and others, (2017) Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC. Nature Physics, 13. pp. 852-858. ISSN 1745-2473

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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 (Pb)ions. Using 480 μ 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 γγ→γγ reaction. A total of 13 candidate events are 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 E T > 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 Standard Model predictions.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Experimental Particle Physics Research Group
Subjects: Q Science > QC Physics
Depositing User: Alice Jackson
Date Deposited: 13 Nov 2018 16:45
Last Modified: 13 Nov 2018 16:46
URI: http://srodev.sussex.ac.uk/id/eprint/80148

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