학술논문
Measurement of the cross-section ratio $\sigma_{\psi(2S )}/\sigma_{J/\psi(1S )}$ in exclusive photoproduction at HERA
Document Type
Working Paper
Author
ZEUS Collaboration; 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.; Onishchuk, Yu.; 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.; Abdullah, W. A. T. Wan; Wichmann, K.; Wing, M.; Yamada, S.; Yamazaki, Y.; Żarnecki, A. F.; Zenaiev, O.
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Abstract
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.
Comment: 31 pages, 9 figures. Updated according to comments from journal referee including a new table. Added full collaboration author list
Comment: 31 pages, 9 figures. Updated according to comments from journal referee including a new table. Added full collaboration author list