Measurement of the cross-section ratio σ<inf>ψ(2S)</inf> /σ<inf>J/ψ(1S)</inf> in exclusive photoproduction at HERA

Abt, I, Adamus, M, Aggarwal, R, Aushev, V, Behnke, O, Bertolin, A, Bloch, I, Brock, I, Brook, N ORCID: https://orcid.org/0000-0002-1818-0113, Brugnera, R, Bruni, A, Bussey, PJ, Caldwell, A, Catterall, CD, Chwastowski, J, Ciborowski, J, Ciesielski, R, Cooper-Sarkar, AM, Corradi, M, Dementiev, RK, Dusini, S, Ferrando, J, Foster, B, Gallo, E, Gangadharan, D, Garfagnini, A, Geiser, A, Grzelak, G, Gwenlan, C, Hochman, D, Jomhari, NZ, Kadenko, I, Karshon, U, Kaur, P, Klanner, R, Klein, U, Korzhavina, IA, Kovalchuk, N, Kuze, M, Levchenko, BB, Levy, A, Löhr, B, Lohrmann, E, Longhin, A, Lorkowski, F, Makarenko, I, Malka, J, Masciocchi, S, Nagano, K, Nam, JD, Onishchuk, Y, Paul, E, Pidhurskyi, I, Polini, A, Przybycień, M, Quintero, A, Rubinsky, I, Ruspa, M, Schneekloth, U, Schörner-Sadenius, T, Selyuzhenkov, I, Shchedrolosiev, M, Shcheglova, LM, Skillicorn, IO, Słomiński, W, Solano, A, Stanco, L, Stefaniuk, N, Surrow, B, Tokushuku, K, Tomaszewska, J, Trofymov, A, Turkot, O, Tymieniecka, T, Verbytskyi, A, Wan Abdullah, WAT, Wichmann, K, Wing, M, Yamada, S, Yamazaki, Y, Żarnecki, AF and Zenaiev, O (2022) Measurement of the cross-section ratio σ<inf>ψ(2S)</inf> /σ<inf>J/ψ(1S)</inf> in exclusive photoproduction at HERA. The Journal of High Energy Physics, 2022 (12). p. 164. ISSN 1126-6708

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Abstract

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.