• Energy Research

We present a measurement of the inelastic, non diffractive J/$��$ photoproduction cross section in the reaction $e^{+} p \to e^{+} {J}/��X$ with the ZEUS detector at HERA. The J/$��$ was identified using both the $��^{+}��^{-}$ 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/$��$ hadroproduction, are not consistent with the data. 31 pages including 7 figures

We present a measurement of the inelastic, non diffractive J/$��$ photoproduction cross section in the reaction $e^{+} p \to e^{+} {J}/��X$ with the ZEUS detector at HERA. The J/$��$ was identified using both the $��^{+}��^{-}$ 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/$��$ hadroproduction, are not consistent with the data. 31 pages including 7 figures