Abstract
This paper reports the cross section measurements for the process ep \rightarrow e~\jpsi~p for Q^2 < 4 GeV^2 at \sqrt s = 296 GeV, based on an integrated luminosity of about 0.5~pb^{-1}, using the ZEUS detector. The \jpsi~was detected in its \rm e^{+}e^{-} and \rm \mu^{+}\mu^{-} decay modes. The photoproduction cross section was measured to be 52^{ \ +7}_{-12}\pm 10~nb at an average \gammap centre of mass energy of 67 GeV and 71^{+13}_{-20}\pm 12~nb at 114 GeV. The significant rise of the cross section compared to lower energy measurements is not in agreement with VDM models, but can be described by QCD inspired models if a rise in the gluon momentum density at low x in the proton is assumed.