Events with largeETtotin photoproduction at HERA

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Abstract
Hard photoproduction events observed at HERA have a large excesses of transverse energy flow with respect to theoretical predictions. For this paper events with total transverse energy greater than 45 GeV were selected. Jet cross sections and the dependence of the event rate on the photon-proton centre of mass energy W were measured. A multi-parton interaction model can describe the jet cross section but probably not the W distribution while a model without multi-parton interactions describes the W dependence well but not the jet cross section. At the moment, there is no model that describes data satisfactorily in the measured kinematic range.