Exclusive photoproduction of Upsilon mesons at HERA

                       ZEUS Collaboration
 
                           Abstract 

The exclusive photoproduction reaction gamma p -> Upsilon p has been 
studied with the ZEUS experiment in ep collisions at HERA using an 
integrated luminosity of 468 pb-1. The measurement covers the kinematic 
range 60 < W < 220 GeV and Q^2 < 1 GeV^2, where W is the photon-proton 
centre-of-mass energy and Q^2 is the photon virtuality. The gamma-p cross 
section for Upsilon photoproduction is presented as a function of W and 
|t|, where t is negative transverse momentum square at the proton vertex. 
These results, which represent the analysis of the full ZEUS data sample 
for dimuon decay channel, are compared to predictions based on 
perturbative QCD.