CROSS-SECTION RATIO OF THE CHARMONIA STATES (2S) AND J/(1S) IN EXCLUSIVE PHOTOPRODUCTION AT HERA

The exclusive photoproduction reactions gamma*p -> J/psi(1S)p and gamma*p -> psi(2S)p have been measured with the ZEUS detector at the HERA collider. The used data sample corresponds to an integrated luminosity of 373 pb(-1) collected during the HERA-II running period. The analysis was performed in the kinematic range of 30 < W < 180 GeV, Q(2) < 1 GeV2, and vertical bar t vertical bar < 1 GeV2, where W is the photon-proton centre-of-mass energy, Q(2) is the virtuality of the photon (gamma*), and t is the squared four-momentum transfer at the proton vertex. The following decay channels were investigated: J/psi(1S) -> mu(+)mu(-), psi(2S) -> mu(+)mu(-), and psi(2S) -> J/psi(1S)pi(+)pi(-) with subsequent decay J/psi(1S) -> mu(+)mu(-).