Prompt Photons in Photoproduction at HERA

Abstract

First inclusive measurements of isolated prompt photons in photoproduction at HERA have been made with the ZEUS detector. Cross sections are given as a function of the pseudorapidity and the transverse energy of the photon, for E_T^gamma > 5 GeV in the gamma-p centre-of-mass energy range 134-285 GeV. Comparisons are made with predictions from LO Monte Carlo models and NLO QCD calculations. For forward eta^gamma (proton direction) good agreement is found, but in the rear direction all predictions fall below the data.