Measurement of the cross-section ratio σψ(2³§) /σ´³/ψ(1³§) in exclusive photoproduction at HERA
Journal of High Energy Physics 2022:12 (2022)
Authors:
I Abt, M Adamus, R Aggarwal, V Aushev, O Behnke, A Bertolin, I Bloch, I Brock, NH Brook, R Brugnera, A Bruni, PJ Bussey, A Caldwell, CD Catterall, J Chwastowski, J Ciborowski, R Ciesielski, AM Cooper-Sarkar, M Corradi, RK Dementiev, S Dusini, J Ferrando, B Foster, E Gallo, D Gangadharan, A Garfagnini, A Geiser, G Grzelak, C Gwenlan, D Hochman, NZ Jomhari, I Kadenko, U Karshon, P Kaur, R Klanner, U Klein, IA Korzhavina, N Kovalchuk, M Kuze, BB Levchenko, A Levy, B Löhr, E Lohrmann, A Longhin, F Lorkowski, I Makarenko, J Malka, S Masciocchi, K Nagano, JD Nam, Y Onishchuk, E Paul, I Pidhurskyi, A Polini, M Przybycień, A Quintero, I Rubinsky, M Ruspa, U Schneekloth, T Schörner-Sadenius, I Selyuzhenkov, M Shchedrolosiev, LM Shcheglova, IO Skillicorn, W Słomiński, A Solano, L Stanco, N Stefaniuk, B Surrow, K Tokushuku, J Tomaszewska, A Trofymov, O Turkot, T Tymieniecka, A Verbytskyi, WAT Wan Abdullah, K Wichmann, M Wing, S Yamada, Y Yamazaki, AF Żarnecki, O Zenaiev
Abstract:
The exclusive photoproduction reactions γp → ´³/ψ(1³§)p and γp → ψ(2³§)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 ´³/ψ(1³§) → μ+μ−, ψ(2³§) → μ+μ− and ψ(2³§) → ´³/ψ(1³§)Ï€+π− with subsequent decay ´³/ψ(1³§) → μ+μ−. The ratio of the production cross sections, R = σψ(2³§)/σ´³/ψ(1³§), 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.
