Eur. Phys. J. C (2013) 73:2466 DOI 10.1140/epjc/s10052-013-2466-y Regular Article - Experimental Physics Elastic and proton-dissociative photoproduction of J/ψ mesons at HERA The H1 Collaboration C. Alexa6, V. Andreev26, A. Baghdasaryan38, S. Baghdasaryan38, W. Bartel12, K. Begzsuren35, A. Belousov26, P. Belov 12, V. Boudry29, I. Bozovic-Jelisavcic2, G. Brandt42, M. Brinkmann12, V. Brisson28, D. Britzger12, A. Buniatyan15, A. Bylinkin25,g, L. Bystritskaya25, A.J. Campbell12, K.B. Cantun Avila23, F. Ceccopieri4,5, K. Cerny32, V. Chekelian27, J.G. Contreras23, J. Cvach31, J.B. Dainton19,K.Daum37,a,b,E.A.DeWolf4,5, C. Diaconu22, M. Dobre6, V. Dodonov14, A. Dossanov13,27, G. Eckerlin12,S.Egli36,E.Elsen12, L. Favart4,5, A. Fedotov25,R.Felst12, J. Feltesse11, J. Ferencei17, D.-J. Fischer12, M. Fleischer12, A. Fomenko26, E. Gabathuler19, J. Gayler12, S. Ghazaryan12, A. Glazov12,L.Goerlich8, N. Gogitidze26, M. Gouzevitch12,c,C.Grab40, A. Grebenyuk12, T. Greenshaw19, G. Grindhammer27, S. Habib12, D. Haidt12, R.C.W. Henderson18, E. Hennekemper16, M. Herbst16, G. Herrera24, M. Hildebrandt36, K.H. Hiller39, J. Hladky`31, D. Hoffmann22, R. Horisberger36, T. Hreus4,5, F. Huber15, M. Jacquet28, X. Janssen4,5,L.Jönsson21, H. Jung12,4,5, M. Kapichine10, C. Kiesling27,M.Klein19, C. Kleinwort12, R. Kogler13,P.Kostka39, M. Krämer12, J. Kretzschmar19, K. Krüger12, M.P.J. Landon20, W. Lange39, P. Laycock19, A. Lebedev26, S. Levonian12, K. Lipka12,f,B.List12,J.List12, B. Lobodzinski12, R. Lopez-Fernandez24, V. Lubimov25,∗,E.Malinovski26, H.-U. Martyn1, S.J. Maxfield19, A. Mehta19,A.B.Meyer12, H. Meyer37, J. Meyer12, S. Mikocki8, I. Milcewicz-Mika8, A. Morozov10, J.V. Morris7, K. Müller41, Th. Naumann39,P.R.Newman3, C. Niebuhr12, D. Nikitin10,G.Nowak8,K.Nowak13,J.E.Olsson12, D. Ozerov12,P.Pahl12, V. Palichik10, M. Pandurovic2, C. Pascaud28, G.D. Patel19,E.Perez11,d, A. Petrukhin12, I. Picuric30, H. Pirumov15,D.Pitzl12,R.Placakytˇ e˙12,f, B. Pokorny32, R. Polifka32,h, V. Radescu12,f, N. Raicevic30, T. Ravdandorj35,P.Reimer31,E.Rizvi20, P. Robmann41, R. Roosen4,5, A. Rostovtsev25, M. Rotaru6, J.E. Ruiz Tabasco23, S. Rusakov26, D. Šálek32, D.P.C. Sankey7, M. Sauter15, E. Sauvan22,i, S. Schmitt12, L. Schoeffel11, A. Schöning15, H.-C. Schultz-Coulon16, F. Sefkow12, S. Shushkevich12, Y. Soloviev12,26, P. Sopicki8, D. South12, V. Spaskov10, A. Specka29,Z.Staykova4,5, M. Steder12,B.Stella33, G. Stoicea6, U. Straumann41, T. Sykora4,5,32, P.D. Thompson3, D. Traynor20, P. Truöl41,I.Tsakov34, B. Tseepeldorj35,e, J. Turnau8, A. Valkárová32, C. Vallée22, P. Van Mechelen4,5, Y. Vazdik26, D. Wegener9, E. Wünsch12,J.Žácekˇ 32, J. Zálešák31, Z. Zhang28,R.Žlebcíkˇ 32, H. Zohrabyan38,F.Zomer28 1I. Physikalisches Institut der RWTH, Aachen, Germany 2Vinca Institute of Nuclear Sciences, University of Belgrade, 1100 Belgrade, Serbia 3School of Physics and Astronomy, University of Birmingham, Birmingham, UKk 4Inter-University Institute for High Energies ULB-VUB, Brussels, Belgiuml 5Universiteit Antwerpen, Antwerpen, Belgiuml 6National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest, Romaniat 7Rutherford Appleton Laboratory, STFC, Didcot, Oxfordshire, UKk 8Institute for Nuclear Physics, Cracow, Polandm 9Institut für Physik, TU Dortmund, Dortmund, Germanyj 10Joint Institute for Nuclear Research, Dubna, Russia 11CEA, DSM/Irfu, CE-Saclay, Gif-sur-Yvette, France 12DESY, Hamburg, Germany 13Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germanyj 14Max-Planck-Institut für Kernphysik, Heidelberg, Germany 15Physikalisches Institut, Universität Heidelberg, Heidelberg, Germanyj 16Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germanyj 17Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak Republicn 18Department of Physics, University of Lancaster, Lancaster, UKk 19Department of Physics, University of Liverpool, Liverpool, UKk 20School of Physics and Astronomy, Queen Mary, University of London, London, UKk 21Physics Department, University of Lund, Lund, Swedeno 22CPPM, Aix-Marseille Univ, CNRS/IN2P3, 13288 Marseille, France 23Departamento de Fisica Aplicada, CINVESTAV, Mérida, Yucatán, Méxicor Page 2 of 17 Eur. Phys. J. C (2013) 73:2466 24Departamento de Fisica, CINVESTAV IPN, México City, Méxicor 25Institute for Theoretical and Experimental Physics, Moscow, Russias 26Lebedev Physical Institute, Moscow, Russia 27Max-Planck-Institut für Physik, München, Germany 28LAL, Université Paris-Sud, CNRS/IN2P3, Orsay, France 29LLR, Ecole Polytechnique, CNRS/IN2P3, Palaiseau, France 30Faculty of Science, University of Montenegro, Podgorica, Montenegrou 31Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republicp 32Faculty of Mathematics and Physics, Charles University, Praha, Czech Republicp 33Dipartimento di Fisica, Università di Roma Tre and INFN Roma 3, Roma, Italy 34Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria 35Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia 36Paul Scherrer Institut, Villigen, Switzerland 37Fachbereich C, Universität Wuppertal, Wuppertal, Germany 38Yerevan Physics Institute, Yerevan, Armenia 39DESY, Zeuthen, Germany 40Institut für Teilchenphysik, ETH, Zürich, Switzerlandq 41Physik-Institut der Universität Zürich, Zürich, Switzerlandq 42Department of Physics, Oxford University, Oxford, UKk Received: 18 April 2013 / Revised: 23 May 2013 / Published online: 15 June 2013 © The Author(s) 2013. This article is published with open access at Springerlink.com Abstract Cross sections for elastic and proton-dissociative t-dependences are parametrised using phenomenological photoproduction of J/ψ mesons are measured with the H1 fits. detector in positron-proton collisions at HERA.√ The data ≈ were√ collected at ep centre-of-mass energies s 318 GeV and s ≈ 225 GeV, corresponding to integrated lumi- 1 Introduction nosities of L = 130 pb−1 and L = 10.8pb−1, respec- tively. The cross sections are measured as a function of the This paper reports a measurement of diffractive J/ψ photo- photon-proton centre-of-mass energy in the range 25 <Wγp production in positron-proton interactions at HERA, < 110 GeV. Differential cross sections dσ/dt, where t is ep → eJ/ψX. For the elastic regime X denotes a proton, the squared four-momentum transfer at the proton vertex, whereas for the proton-dissociative regime X denotes a 2 are measured in the range |t| < 1.2GeV for the elastic proton-dissociative system Y of mass mp <MY < 10 GeV, process and |t| < 8GeV2 for proton dissociation. The re- as depicted in Fig. 1. sults are compared to other measurements. The Wγp and Diffractive vector meson production is characterised by the t-channel exchange of a colourless object between the incoming photon and proton. In the high-energy limit Regge a e-mail: [email protected] bAlso at Rechenzentrum, Universität Wuppertal, Wuppertal, Germany. lSupported by FNRS-FWO-Vlaanderen, IISN-IIKW and IWT and by cAlso at IPNL, Université Claude Bernard Lyon 1, CNRS/IN2P3, Interuniversity Attraction Poles Programme, Belgian Science Policy. Villeurbanne, France. mPartially Supported by Polish Ministry of Science and Higher Educa- dAlso at CERN, Geneva, Switzerland. tion, grant DPN/N168/DESY/2009. eAlso at Ulaanbaatar University, Ulaanbaatar, Mongolia. nSupported by VEGA SR grant no. 2/7062/ 27. fSupported by the Initiative and Networking Fund of the Helmholtz oSupported by the Swedish Natural Science Research Council. Association (HGF) under the contract VH-NG-401 and S0-072. pSupported by the Ministry of Education of the Czech Republic under gAlso at Moscow Institute of Physics and Technology, Moscow, Rus- the projects LC527, INGO-LA09042 and MSM0021620859. sia. qSupported by the Swiss National Science Foundation. hAlso at Department of Physics, University of Toronto, Toronto, On- r tario, Canada M5S 1A7. Supported by CONACYT, México, grant 48778-F. s iAlso at LAPP, Université de Savoie, CNRS/IN2P3, Annecy-le-Vieux, Russian Foundation for Basic Research (RFBR), grant no France. 1329.2008.2 and Rosatom. t jSupported by the Bundesministerium für Bildung und Forschung, Supported by the Romanian National Authority for Scientific Re- FRG, under contract numbers 05H09GUF, 05H09VHC, 05H09VHF, search under the contract PN 09370101. 05H16PEA. uPartially Supported by Ministry of Science of Montenegro, no. 05- kSupported by the UK Science and Technology Facilities Council, and 1/3-3352. formerly by the UK Particle Physics and Astronomy Research Council. ∗Deceased. Eur. Phys. J. C (2013) 73:2466 Page 3 of 17 √ ≈ energy of s 318√ GeV, data recorded at a lower centre- of-mass energy of s ≈ 225 GeV are analysed. This low- energy data set extends the kinematic region in Wγp into the transition region between previous diffractive J/ψ measure- ments at HERA and fixed target experiments [26, 27]. The elastic and proton-dissociative cross sections as functions of t and Wγp are subjected to phenomenological fits, together Fig. 1 Diffractive J/ψ meson production in electron proton colli- with previous H1 data [4, 24], and are compared with QCD sions: (a) elastic J/ψ production in which the proton stays intact and based dipole models [14]. (b) proton-dissociative J/ψ production in which the proton dissociates to a low mass excited state with mass MY >mp 2 Experimental method theory predicts [1, 2] an approximate cross section depen- ∝ δ dence σ Wγp as a function of the photon-proton centre- 2.1 Kinematics of-mass energy Wγp. For elastic production of light vec- tor mesons (ρ, ω, φ)