Measurement of Inelastic J/Psi Photoproduction at HERA

Abstract

We present a measurement of the inelastic, non diffractive J/$ψ$ photoproduction cross section in the reaction $e^{+} p \to e^{+} {J}/ψX$ with the ZEUS detector at HERA. The J/$ψ$ was identified using both the $μ^{+}μ^{-}$ and $e^{+}e^{-}$ decay channels and events were selected within the range $0.4 1$ GeV$^2$, NLO calculations of the photon-gluon fusion process based on the colour-singlet model are in good agreement with the data. The predictions of a specific leading order colour-octet model, as formulated to describe the CDF data on J/$ψ$ hadroproduction, are not consistent with the data.