The exclusive photoproduction reactions γp → J/ψ(1S)p and γp → ψ(2S)p have been measured at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373 pb−1. The measurement was made in the kinematic range 30 < W < 180 GeV, Q2 < 1 GeV2 and |t| < 1 GeV2, where W is the photon-proton centre-of-mass energy, Q2 is the photon virtuality and t is the squared four-momentum transfer at the proton vertex. The decay channels used were J/ψ(1S) → μ+μ−, ψ(2S) → μ+μ− and ψ(2S) → J/ψ(1S)π+π− with subsequent decay J/ψ(1S) → μ+μ−. The ratio of the production cross sections, R = σψ(2S)/σJ/ψ(1S), has been measured as a function of W and |t| and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production, which are in reasonable agreement with the data.
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INFN Padova, Padova, Italy; Dipartimento di Fisica e Astronomia dell’ Università and INFN, Padova, Italy; INFN Bologna, Bologna, Italy; Università del Piemonte Orientale, Novara, and INFN, Torino, Italy; Università di Torino and INFN, Torino, Italy (Supported by the Italian National Institute for Nuclear Physics (INFN))
Physikalisches Institut der Universität Bonn, Bonn, Germany (Supported by the German Federal Ministry for Education and Research (BMBF), under contract No. 05 H09PDF)
Physics and Astronomy Department, University College London, London, United Kingdom; School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom; Department of Physics, University of Oxford, Oxford, United Kingdom (Supported by the Science and Technology Facilities Council, UK)
Department of Physics, York University, Ontario, Canada M3J 1P3 (Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC))
Hamburg University, Institute of Experimental Physics, Hamburg, Germany (Supported by the German Federal Ministry for Education and Research (BMBF), under contract No. 05h09GUF, and the SFB 676 of the Deutsche Forschungsgemeinschaft (DFG))
Department of Physics, Tokyo Institute of Technology, Tokyo, Japan; Institute of Particle and Nuclear Studies, KEK, Tsukuba, Japan; Department of Physics, Kobe University, Kobe, Japan (Supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and its grants for Scientific Research)
Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics, Tel Aviv University, Tel Aviv, Israel (Supported by the Israel Science Foundation)
Department of Physics, Temple University, Philadelphia, PA 19122, USA (Supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science)
Department of Physics, Jagellonian University, Krakow, Poland (Supported by the Polish National Science Centre (NCN) grant no. DEC-2014/13/B/ST2/02486)
National Centre for Particle Physics, Universiti Malaya, 50603 Kuala Lumpur, Malaysia (Supported by HIR grant UM.C/625/1/HIR/149 and UMRG grants RU006-2013, RP012A-13AFR and RP012B-13AFR from Universiti Malaya, and ERGS grant ER004-2012A from the Ministry of Education, Malaysia)
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Supported by a Leverhulme Trust Emeritus Fellowship (B. Foster)
Supported by DESY, Hamburg, Germany (M. Wing)
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The ZEUS collaboration., Abt, I., Adamus, M. et al. Measurement of the cross-section ratio σψ(2S)/σJ/ψ(1S) in exclusive photoproduction at HERA. J. High Energ. Phys. 2022, 164 (2022). https://doi.org/10.1007/JHEP12(2022)164
- Heavy Quark Production
- Lepton-Nucleon Scattering