Observation of Light-by-Light Scattering in Ultraperipheral Pb+Pb Collisions with the ATLAS Detector

This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at sNN=5.02 TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73 nb-1, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-li...

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Hauptverfasser:	Adelman, J, Affolder, A. A, Akatsuka, S, Amor Dos Santos, S. P, Anastopoulos, C, Azoulay, A. M, Banas, E, Beddall, A, Begel, M, Benekos, N, Breaden Madden, W. D, Caforio, D, Casper, D. W, Cheremushkina, E, Cherkaoui El Moursli, R, Coniavitis, E, De Vasconcelos Corga, K, Diehl, E. B, Ellert, M, Emeliyanov, D, Feligioni, L, Feng, E. J, Filipčič, A, Foster, A. G, Franchino, S, Gallardo, G. E, Gardner, R. W, Garonne, V, Gaycken, G, Giagu, S, Gladilin, L. K, Gongadze, A, Gravili, F. G, Guenther, J, Hageböck, S, He, F, Herrmann, M. G, Higashida, A, Hirose, S, Hladik, O, Hrdinka, J, Hu, S, Ikeno, M, Ishitsuka, M, Ivina, A, Jimenez Morales, F. A, Kajomovitz, E, Kisliuk, D. P, Knoops, E. B. F. G, Krasny, M. W, Kuhl, T, Lai, S, Landon, M. P. J, Leblanc, M, Lee, L, Li, S, Liblong, A, Lin, C. Y, Lloyd, S. L, Lohwasser, K, Machado Miguens, J, Maeland, S, Mansoulie, B, Manthos, I, Merola, L, Mina, R. A, Mornacchi, G, Moser, B, Mullier, G. A, Nemethy, P, Ng, Y. S, Nikiforou, N, Novak, T, Nozka, L, Oakham, F. G, Okazaki, Y, Okuyama, T, Panizzo, G, Poggi, R, Polychronakos, V, Prince, S, Prokoshin, F, Ramirez Morales, A, Rauscher, F, Reale, M, Rinaldi, L, Ripellino, G, Rizatdinova, F, Rosin, G, Rozen, Y, Salamanna, G, Sandhoff, M, Sawada, R, Sebastiani, C. D, Serkin, L, Silva Oliveira, M. V, Sinev, N. B, Sopczak, A, Spighi, R, Zinonos, Z
Format:	Artikel
Sprache:	eng
Schlagworte:	ATLAS experiment Integrated luminosity Pseudorapidities Scattering process Selection criteria Standard deviation Transverse energy Transverse momenta
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Zusammenfassung:	This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at sNN=5.02 TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73 nb-1, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy ETγ>3 GeV and pseudorapidity 2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12±3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78±13(stat)±7(syst)±3(lumi) nb.