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

ZEUS Collaboration

Preprint

PUBDB-2022-03175

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

ZEUS Collaboration (Collaboration author)DESY*

2022

[10.3204/PUBDB-2022-03175]

This record in other databases:

Please use a persistent id in citations: doi:10.3204/PUBDB-2022-03175

Report No.: DESY-22-107; arXiv:2206.13343

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.

Keyword(s): vector meson, production ; cross section, ratio ; GeV ; psi(3685) ; photoproduction ; DESY HERA Stor ; deep inelastic scattering ; ZEUS ; photon ; kinematics