Measurement of the cross-section ratio \(\sigma_{\psi(2S )}/\sigma_{J/\psi(1S )}\) in exclusive photoproduction at HERA

• Published in: arXiv.org 2022-12
• Main Authors: Collaboration, ZEUS, Abt, I, Adamus, M, Aggarwal, R, Aushev, V, Behnke, O, Bertolin, A, Bloch, I, Brock, I, Brook, N H, Brugnera, R, Bruni, A, Bussey, P J, Caldwell, A, Catterall, C D, Chwastowski, J, Ciborowski, J, Ciesielski, R, Cooper-Sarkar, A M, Corradi, M, Dementiev, R K, Dusini, S, Ferrando, J, Foster, B, Gallo, E, Gangadharan, D, Garfagnini, A, Geiser, A, Grzelak, G, Gwenlan, C, Hochman, D, Jomhari, N Z, Kadenko, I, Karshon, U, Kaur, P, Klanner, R, Klein, U, Korzhavina, I A, Kovalchuk, N, Kuze, M, Levchenko, B B, Levy, A, Löhr, B, Lohrmann, E, Longhin, A, Lorkowski, F, Makarenko, I, Malka, J, Masciocchi, S, Nagano, K, Nam, J D, Yu Onishchuk, Paul, E, Pidhurskyi, I, Polini, A, Przybycień, M, Quintero, A, Rubinsky, I, Ruspa, M, Schneekloth, U, Schörner-Sadenius, T, Selyuzhenkov, I, Shchedrolosiev, M, Shcheglova, L M, Skillicorn, I O, Słomiński, W, Solano, A, Stanco, L, Stefaniuk, N, Surrow, B, Tokushuku, K, Tomaszewska, J, Trofymov, A, Turkot, O, Tymieniecka, T, Verbytskyi, A, W A T Wan Abdullah, Wichmann, K, Wing, M, Yamada, S, Yamazaki, Y, Żarnecki, A F, Zenaiev, O
• Format: Article
• Language: English
• Subjects: Cross-sections; Decay; Inelastic scattering; Luminosity; Momentum transfer; Particle production; Photons; Photoproduction; Protons; Vector mesons
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2206.13343

The exclusive photoproduction reactions \(\gamma p \to J/\psi(1S) p\) and \(\gamma p \to \psi(2S) p\) 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, \(Q^2 < 1\) GeV\(^2\) and \(|t| < 1\) GeV\(^2\), where \(W\) is the photon--proton centre-of-mass energy, \(Q^2\) is the photon virtuality and \(t\) is the squared four-momentum transfer at the proton vertex. The decay channels used were \(J/\psi(1S) \to \mu^+ \mu^-\), \(\psi(2S) \to \mu^+ \mu^-\) and \(\psi(2S) \to J/\psi(1S) \pi^+ \pi^-\) with subsequent decay \(J/\psi(1S) \to \mu^+ \mu^-\). The ratio of the production cross sections, \(R = \sigma_{\psi(2S)} / \sigma_{J/\psi(1S)}\), 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.