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Coherent $$\mathrm{J}/\psi $$ and $${\uppsi '}$$ photoproduction at midrapidity in ultra-peripheral Pb–Pb collisions at $$\sqrt{s_{\mathrm {NN}}}~=~5.02$$ TeV

S. AcharyaVariable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, IndiaD. AdamováNuclear Physics Institute of the Czech Academy of Sciences, Řež u Prahy, Czech RepublicA. AdlerJohann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik und Mathematik, Frankfurt, GermanyJ. AdolfssonDivision of Particle Physics, Department of Physics, Lund University, Lund, SwedenG. Aglieri RinellaEuropean Organization for Nuclear Research (CERN), Geneva, SwitzerlandM. AgnelloDipartimento DISAT del Politecnico and Sezione INFN, Turin, ItalyN. AgrawalINFN, Sezione di Bologna, Bologna, ItalyZ. AhammedVariable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, IndiaS. AhmadDepartment of Physics, Aligarh Muslim University, Aligarh, IndiaS. U. AhnKorea Institute of Science and Technology Information, Daejeon, Republic of KoreaZaenal AkbarIndonesian Institute of Sciences, Jakarta, IndonesiaA. AkindinovNRC Kurchatov Institute, ITEP, Moscow, RussiaM. Al-TuranyResearch Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, GermanyD. S. D. AlbuquerqueUniversidade Estadual de Campinas (UNICAMP), Campinas, BrazilD. AleksandrovNational Research Centre Kurchatov Institute, Moscow, RussiaB. AlessandroINFN, Sezione di Torino, Turin, ItalyH. M. AlfandaCentral China Normal University, Wuhan, ChinaR. Alfaro MolinaInstituto de Física, Universidad Nacional Autónoma de México, Mexico City, MexicoB. AliDepartment of Physics, Aligarh Muslim University, Aligarh, IndiaY. AliCOMSATS University Islamabad, Islamabad, PakistanA. AliciDipartimento di Fisica e Astronomia dell'Università and Sezione INFN, Bologna, ItalyN. AlizadehvandchaliUniversity of Houston, Houston, TX, USAA. AlkinEuropean Organization for Nuclear Research (CERN), Geneva, SwitzerlandJ. AlmeDepartment of Physics and Technology, University of Bergen, Bergen, NorwayT. AltDepartment of Physics and Technology, University of Bergen, Bergen, NorwayL. AltenkamperDepartment of Physics and Technology, University of Bergen, Bergen, NorwayI. AltsybeevSt. Petersburg State University, St. Petersburg, RussiaM. N. AnaamCentral China Normal University, Wuhan, ChinaC. AndreiHoria Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, RomaniaD. AndreouNikhef, National Institute for Subatomic Physics, Amsterdam, The NetherlandsA. AndronicInstitut für Kernphysik, Westfälische Wilhelms-Universität Münster, Münster, GermanyV. AnguelovPhysikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyT. AntičićRudjer Bošković Institute, Zagreb, CroatiaF. AntinoriINFN, Sezione di Padova, Padua, ItalyP. AntonioliINFN, Sezione di Bologna, Bologna, ItalyC. AnujDepartment of Physics, Aligarh Muslim University, Aligarh, IndiaN. ApadulaLawrence Berkeley National Laboratory, Berkeley, CA, USAL. AphecetcheSUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, FranceH. AppelshäuserInstitut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, GermanyS. ArcelliDipartimento di Fisica e Astronomia dell'Università and Sezione INFN, Bologna, ItalyR. ArnaldiINFN, Sezione di Torino, Turin, ItalyM. ArratiaLawrence Berkeley National Laboratory, Berkeley, CA, USAI. C. ArseneDepartment of Physics, University of Oslo, Oslo, NorwayM. ArslandokPhysikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyA. AugustinusEuropean Organization for Nuclear Research (CERN), Geneva, SwitzerlandR. AverbeckResearch Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, GermanyS. AzizLaboratoire de Physique des 2 Infinis, Irène Joliot-Curie, Orsay, FranceM. D. AzmiDepartment of Physics, Aligarh Muslim University, Aligarh, IndiaA. BadaláINFN, Sezione di Catania, Catania, ItalyY. W. BaekGangneung-Wonju National University, Gangneung, Republic of KoreaXiaoshuan BaiResearch Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, GermanyR. BailhacheInstitut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, GermanyR. BalaPhysics Department, University of Jammu, Jammu, IndiaA. BalbinoDipartimento DISAT del Politecnico and Sezione INFN, Turin, ItalyA. BaldisseriDépartment de Physique Nucléaire (DPhN), Université Paris-Saclay Centre d'Etudes de Saclay (CEA), IRFU, Saclay, FranceM. BallHelmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, GermanyD. BanerjeeDepartment of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Bose Institute, Kolkata, IndiaR. BarberaDipartimento di Fisica e Astronomia dell'Università and Sezione INFN, Catania, ItalyL. BarioglioDipartimento di Fisica dell'Università and Sezione INFN, Turin, ItalyM. BarlouDepartment of Physics, School of Science, National and Kapodistrian University of Athens, Athens, GreeceG. G. BarnaföldiWigner Research Centre for Physics, Budapest, HungaryL. S. BarnbyNuclear Physics Group, STFC Daresbury Laboratory, Daresbury, UKV. BarretUniversité Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, FranceC. BartelsUniversity of Liverpool, Liverpool, UKKlaus BarthEuropean Organization for Nuclear Research (CERN), Geneva, SwitzerlandE. BartschInstitut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, GermanyF. BaruffaldiDipartimento di Fisica e Astronomia dell'Università and Sezione INFN, Padova, ItalyN. BastidUniversité Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, FranceS. BasuDivision of Particle Physics, Department of Physics, Lund University, Lund, SwedenG. BatigneSUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, FranceB. BatyunyaJoint Institute for Nuclear Research (JINR), Dubna, RussiaD. BauriIndian Institute of Technology Bombay (IIT), Mumbai, IndiaJ. L. Bazo AlbaSección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, PeruI. G. BeardenNiels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkC. BeattieYale University, New Haven, CT, USAI. BelikovUniversité de Strasbourg, CNRS, IPHC UMR 7178, 67000, Strasbourg, FranceA. D. C. Bell HechavarriaInstitut für Kernphysik, Westfälische Wilhelms-Universität Münster, Münster, GermanyF. BelliniEuropean Organization for Nuclear Research (CERN), Geneva, SwitzerlandR. BellwiedUniversity of Houston, Houston, TX, USAS. BelokurovaSt. Petersburg State University, St. Petersburg, RussiaV. BelyaevNRNU Moscow Engineering Physics Institute, Moscow, RussiaG. BencédiInstituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, MexicoS. BeolèDipartimento di Fisica dell'Università and Sezione INFN, Turin, ItalyA. BercuciHoria Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, RomaniaY. BerdnikovPetersburg Nuclear Physics Institute, Gatchina, RussiaA. BerdnikovaPhysikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyD. BerényiWigner Research Centre for Physics, Budapest, HungaryL. BergmannPhysikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, GermanyMihaela Gabriela BesoiuInstitute of Space Science (ISS), Bucharest, RomaniaL. BetevEuropean Organization for Nuclear Research (CERN), Geneva, SwitzerlandPartha Pratim BhaduriVariable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, IndiaA. BhasinPhysics Department, University of Jammu, Jammu, IndiaI. R. BhatPhysics Department, University of Jammu, Jammu, IndiaM. A. BhatDepartment of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Bose Institute, Kolkata, IndiaB. BhattacharjeeDepartment of Physics, Gauhati University, Guwahati, IndiaP. BhattacharyaDipartimento di Fisica dell'Università and Sezione INFN, Cagliari, ItalyA. BianchiDipartimento di Fisica dell'Università and Sezione INFN, Turin, ItalyL. BianchiDipartimento di Fisica dell'Università and Sezione INFN, Turin, ItalyN. BianchiDipartimento di Fisica dell'Università and Sezione INFN, Turin, ItalyJ. BielčíkFaculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic

2021en

ABI

Annotatsiya

Abstract The coherent photoproduction of $$\mathrm{J}/\psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> </mml:mrow> </mml:math> and $${\uppsi '}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>ψ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> mesons was measured in ultra-peripheral Pb–Pb collisions at a center-of-mass energy $$\sqrt{s_{\mathrm {NN}}}~=~5.02$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:msub> <mml:mi>s</mml:mi> <mml:mi>NN</mml:mi> </mml:msub> </mml:msqrt> <mml:mspace/> <mml:mo>=</mml:mo> <mml:mspace/> <mml:mn>5.02</mml:mn> </mml:mrow> </mml:math> TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $$\mathrm{J}/\psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> </mml:mrow> </mml:math> is reconstructed using the dilepton ( $$l^{+} l^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>l</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>l</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> ) and proton–antiproton decay channels, while for the $${\uppsi '}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>ψ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> the dilepton and the $$l^{+} l^{-} \pi ^{+} \pi ^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>l</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>l</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 $$\mu {\mathrm{b}}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:msup> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . The results are compared with theoretical models for coherent $$\mathrm{J}/\psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> </mml:mrow> </mml:math> and $${\uppsi '}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>ψ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.64 at a Bjorken- x of around $$6\times 10^{-4}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>6</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $$\mathrm{J}/\psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> </mml:mrow> </mml:math> cross section including ALICE measurements at forward rapidity. The ratio of $${\uppsi '}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>ψ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> to $$\mathrm{J}/\psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> </mml:mrow> </mml:math> coherent photoproduction cross sections was also measured and found to be consistent with the one for photoproduction off protons.

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DOI: 10.1140/epjc/s10052-021-09437-6

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