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Observation of Light-by-Light Scattering in Ultraperipheral Pb+Pb Collisions with the ATLAS DetectorAdam Bourdarios, C; Aguilar-Saavedra, J A; Ahmadov, F; Alberghi, G L; Alonso, A; Anelli, C R; Becker, M; Bentvelsen, S; Berta, P; Bertram, I A; Biglietti, M; Bjørke, K; Blocker, C; Bocci, A; Bokan, P; Bruni, G; Caforio, D; Cai, H; Cantero, J; Ceradini, F; Cioară, I A; Crescioli, F; Dam, M; D'Amico, V; Dandoy, J R; Dang, N P; De Maria, A; De Vasconcelos Corga, K; Demichev, M; Donadelli, M; Dysch, S; Eigen, G; El Kacimi, M; Farilla, A; Fusayasu, T; Gonella, L; Gorini, B; Goussiou, A G; Grud, C; Hamano, K; Hayward, H S; Jarlskog, G; Jones, R W L; Kahra, C; Kluth, S; Kobel, M; La Ruffa, F; Laforge, B; Lösle, A; Maček, B; Mc Kee, S P; Meyer, J-P; Monk, J; Monnier, E; Novgorodova, O; Oerdek, S; Oleiro Seabra, L F; Oreglia, M J; Pandini, C E; Papadatos, C; Parodi, F; Peters, R F Y; Petridou, C; Pollard, C S; Prokoshin, F; Robson, A; Roe, S; Rosbach, K; Rosser, B J; Rossi, E; Rossini, L; Rybar, M; Sadykov, R; Salvatore, F; Sauvan, E; Savic, N; Sbrizzi, A; Shabalina, E; Shi, L; Slovak, R; Stroynowski, R; Ta, D; Tapprogge, S; Timoshenko, S; Tokushuku, K; Trofymov, A; Tseng, J C-L; Urquijo, P; Vachon, B; Veatch, J; Wahlberg, H; Walkowiak, W; Wengler, T; Wölker, R W; Zakharchuk, N; Zhou, Y; Zhu, Y; Zhulanov, V; Zinonos, Z; Ziolkowski, M
Physical review letters, 2019-Aug-02, Letnik: 123, Številka: 5Journal Article
This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at sqrts_{NN}=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 E_{T}^{γ}>3 GeV and pseudorapidity |η_{γ}|<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.
