Abstract submitted to the
         XXXth International Conference on High Energy Physics
                July 27 - August 2, 2000, Osaka, Japan
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                The structure of the photon and the dynamics of
          resolved photon processes in dijet photoproduction at HERA

                    
                               ZEUS Collaboration



                                    Abstract


    Dijet photoproduction has been measured with the ZEUS detector at
HERA using an integrated luminosity of 38 pb^-1. Jets with E_T^jet >
14 GeV are identified by means of a k_T-cluster
algorithm. Differential cross sections are presented as a function of
x_gamma^obs, the fraction of the photon's energy participating in the
production of the two jets of highest transverse energy, and
cos(theta^*), the angle between the dijet and beam axes in the dijet
centre-of-mass system.  Comparisons to next-to-leading order QCD
calculations show that the theory underestimates the data for
low-x_gamma^obs, indicating inadequacies in the photon structure
parameterisations.  However, the shape of the cross section in
cos(theta^*) is well described, confirming the validity of the
parton-parton dynamics in the QCD calculations.