Dijets in Diffractive Photoproduction at HERA
---------------------------------------------

A measurement is presented of differential dijet cross sections in low-|t| diffractive photoproduction processes of the type ep -> eXY, in which the photon dissociation system X is separated from a leading low-mass baryonic system Y by a large rapidity gap. The measurement is based on an integrated luminosity of 18 pb^-1. Dijet events are identified using the inclusive k_T cluster algorithm. The cross sections are given at the level of stable hadrons and correspond to the kinematic range Q^2 < 0.01 GeV^2, 165 < W < 240 GeV, \xpom < 0.03, E_T (jet1) > 5 GeV and E_T (jet2) > 4 GeV. The measurements are compared with predictions based on diffractive parton distributions obtained from a QCD analysis of inclusive diffractive DIS and with diffractive dijet production in DIS.