Observation of Light-by-Light Scattering in Ultraperipheral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Pb</mml:mi><mml:mo>+</mml:mo><mml:mi>Pb</mml:mi></mml:mrow></mml:math> Collisions with the ATLAS Detector
G. AadCPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, FranceB. AbbottHomer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma, USAD. C. AbbottDepartment of Physics, University of Massachusetts, Amherst, Massachusetts, USAO. AbdinovInstitute of Physics, Azerbaijan Academy of Sciences, Baku, AzerbaijanA. Abed AbudDipartimento di Fisica, Università di Pavia, Pavia, ItalyKira AbelingII. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, GermanyD. K. AbhayasingheDepartment of Physics, Royal Holloway University of London, Egham, United KingdomHaider AbidiDepartment of Physics, University of Toronto, Toronto, Ontario, CanadaO. S. AbouZeidNiels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkN. L. AbrahamDepartment of Physics and Astronomy, University of Sussex, Brighton, United KingdomH. AbramowiczRaymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, IsraelH. AbreuDepartment of Physics, Technion, Israel Institute of Technology, Haifa, IsraelY. AbulaitiHigh Energy Physics Division, Argonne National Laboratory, Argonne, Illinois, USAB. S. AcharyaICTP, Trieste, ItalyB. AchkarII. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, GermanyS. AdachiInternational Center for Elementary Particle Physics and Department of Physics, University of Tokyo, Tokyo, JapanL. AdámekInstitut für Physik, Universität Mainz, Mainz, GermanyClaire Adam BourdariosLAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, FranceL. AdamczykAGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow, PolandJahred AdelmanDepartment of Physics, Northern Illinois University, DeKalb, Illinois, USAM. AdersbergerFakultät für Physik, Ludwig-Maximilians-Universität München, München, GermanyAytul AdiguzelDepartment of Physics, Bogazici University, Istanbul, TurkeyS. AdorniDépartement de Physique Nucléaire et Corpusculaire, Université de Genève, Genève, SwitzerlandTim AdyeParticle Physics Department, Rutherford Appleton Laboratory, Didcot, United KingdomTony AffolderSanta Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, California, USAY. AfikDepartment of Physics, Technion, Israel Institute of Technology, Haifa, IsraelC. AgapopoulouLAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, FranceMerve Nazlim AgarasLPC, Université Clermont Auvergne, CNRS/IN2P3, Clermont-Ferrand, FranceAnamika AggarwalInstitute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, NetherlandsC. AgheorghieseiDepartment of Physics, Alexandru Ioan Cuza University of Iasi, Iasi, RomaniaJ. A. Aguilar–SaavedraLaboratório de Instrumentação e Física Experimental de Partículas-LIP, PortugalF. AhmadovJoint Institute for Nuclear Research, Dubna, RussiaW. S. AhmedDepartment of Physics, McGill University, Montreal, Quebec, CanadaX. AiInstitute of High Energy Physics, Chinese Academy of Sciences, Beijing, ChinaGiulio AielliDipartimento di Fisica, Università di Roma Tor Vergata, Roma, ItalyS. AkatsukaFaculty of Science, Kyoto University, Kyoto, JapanTorsten AkessonFysiska institutionen, Lunds universitet, Lund, SwedenE. AkilliDépartement de Physique Nucléaire et Corpusculaire, Université de Genève, Genève, SwitzerlandAndrei AkimovP.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, RussiaK. Al KhouryLAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, FranceGian Luigi AlberghiINFN Bologna and Universita' di Bologna, Dipartimento di Fisica, ItalyJ. AlbertDepartment of Physics and Astronomy, University of Victoria, Victoria, British Columbia, CanadaM. J. Alconada VerziniInstituto de Física La Plata, Universidad Nacional de La Plata and CONICET, La Plata, ArgentinaSara AlderweireldtCERN, Geneva, SwitzerlandMartin AleksaCERN, Geneva, SwitzerlandI. N. AleksandrovJoint Institute for Nuclear Research, Dubna, RussiaC. AlexaHoria Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, RomaniaD. AlexandreInstitut für Physik, Humboldt Universität zu Berlin, Berlin, GermanyT. AlexopoulosPhysics Department, National Technical University of Athens, Zografou, GreeceA. AlfonsiNikhef National Institute for Subatomic Physics and University of Amsterdam, Amsterdam, NetherlandsMuhammad AlhroobHomer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma, USABabar AliCzech Technical University in Prague, Prague, Czech RepublicGianluca AlimontiINFN Sezione di Milano, ItalyJ. AlisonEnrico Fermi Institute, University of Chicago, Chicago, Illinois, USAS. P. AlkireDepartment of Physics, University of Washington, Seattle, Washington, USAC. AllaireLAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, FranceBenedict AllbrookeDepartment of Physics and Astronomy, University of Sussex, Brighton, United KingdomB. W. AllenCenter for High Energy Physics, University of Oregon, Eugene, Oregon, USAPhilip Patrick AllportSchool of Physics and Astronomy, University of Birmingham, Birmingham, United KingdomA. AloisioDipartimento di Fisica, Università di Napoli, Napoli, ItalyA. AlonsoNiels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkF. AlonsoInstituto de Física La Plata, Universidad Nacional de La Plata and CONICET, La Plata, ArgentinaCristiano AlpigianiDepartment of Physics, University of Washington, Seattle, Washington, USAA. A. AlshehriSUPA-School of Physics and Astronomy, University of Glasgow, Glasgow, United KingdomM. Alvarez EstevezDepartamento de Física Teorica C-15 and CIAFF, Universidad Autónoma de Madrid, Madrid, SpainD. Álvarez PiquerasInstituto de Física Corpuscular (IFIC), Centro Mixto Universidad de Valencia-CSIC, Valencia, SpainM. G. AlviggiDipartimento di Fisica, Università di Napoli, Napoli, ItalyY. Amaral CoutinhoUniversidade Federal do Rio De Janeiro COPPE/EE/IF, Rio de Janeiro, BrazilA. AmblerDepartment of Physics, McGill University, Montreal, Quebec, CanadaL. AmbrozDepartment of Physics, Oxford University, Oxford, United KingdomC. AmelungDepartment of Physics, Brandeis University, Waltham, Massachusetts, USAD. AmideiDepartment of Physics, University of Michigan, Ann Arbor, Michigan, USAS. P. Amor Dos SantosLaboratório de Instrumentação e Física Experimental de Partículas-LIP, PortugalS. AmorosoDeutsches Elektronen-Synchrotron DESY, Hamburg and Zeuthen, GermanyCherifa Sabrina AmroucheDépartement de Physique Nucléaire et Corpusculaire, Université de Genève, Genève, SwitzerlandF. F. AnDepartment of Physics and Astronomy, Iowa State University, Ames, Iowa, USAChristos AnastopoulosDepartment of Physics and Astronomy, University of Sheffield, Sheffield, United KingdomN. AndariIRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, FranceT. AndeenDepartment of Physics, University of Texas at Austin, Austin, Texas, USAC. F. AndersPhysikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyJohn Kenneth AndersAlbert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics, University of Bern, Bern, SwitzerlandA. AndreazzaDipartimento di Fisica, Università di Milano, Milano, ItalyV. AndreiKirchhoff-Institut für Physik, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyC. R. AnelliDepartment of Physics and Astronomy, University of Victoria, Victoria, British Columbia, CanadaS. AngelidakisLPC, Université Clermont Auvergne, CNRS/IN2P3, Clermont-Ferrand, FranceAaron AngeramiNevis Laboratory, Columbia University, Irvington, New York, USAAlexey AnisenkovBudker Institute of Nuclear Physics and NSU, SB RAS, Novosibirsk, RussiaA. AnnoviINFN Sezione di Pisa, ItalyC. AntelKirchhoff-Institut für Physik, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyM. T. AnthonyDepartment of Physics and Astronomy, University of Sheffield, Sheffield, United KingdomM. AntonelliINFN e Laboratori Nazionali di Frascati, Frascati, ItalyD. J. A. AntrimDepartment of Physics and Astronomy, University of California Irvine, Irvine, California, USAFabio AnulliINFN Sezione di Roma, ItalyMasato AokiKEK, High Energy Accelerator Research Organization, Tsukuba, JapanJ. A. Aparisi PozoInstituto de Física Corpuscular (IFIC), Centro Mixto Universidad de Valencia-CSIC, Valencia, SpainL. Aperio BellaCERN, Geneva, SwitzerlandG. ArabidzeDepartment of Physics and Astronomy, Michigan State University, East Lansing, Michigan, USAJ. P. AraqueLaboratório de Instrumentação e Física Experimental de Partículas-LIP, PortugalV. Araujo FerrazUniversidade Federal do Rio De Janeiro COPPE/EE/IF, Rio de Janeiro, Brazil
2019lv
ABI
Аннотация
This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at sqrt[s_{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.
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