Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the

\gamma p

centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.

Note:

19 pages, latex, 4 figures appended as uuencoded file Report-no: DESY 94-210

electron p: colliding beams
colliding beams: electron p
exchange: one-photon
one-photon: exchange
photon p: interaction
interaction: photon p
jet: photoproduction
photoproduction: jet
hadron: multiple production
multiple production: hadron

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