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

ZEUS Collaboration, I. Abt, M. Adamus +80

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…