The exclusive photoproduction reactions γp→J/ψ(1S)p and
γp→ψ(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,
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
J/ψ(1S)→μ+μ−, ψ(2S)→μ+μ− and ψ(2S)→J/ψ(1S)π+π− with subsequent decay J/ψ(1S)→μ+μ−. The
ratio of the production cross sections, R=σψ(2S)/σJ/ψ(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 lis