Diffractive Hard Photoproduction at HERA and Evidence for the Gluon Content of the Pomeron

Abstract

Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction $ep\to jet+X$ with quasi-real photons have been measured with the ZEUS detector. The cross sections refer to jets with transverse energies $E_T^{jet}>8$~GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale $\sim (E_T^{jet}{)}^2$. A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30\% and 80\% of the momentum of the pomeron carried by partons is due to hard gluons.

25 pages, latex, 4 figures appended as uuencoded file. No change w.r.t. previous version (just avoiding warning latex messages while processing)

References in corpus (7)

• First Measurement of the Deep--Inelastic Structure of Proton Diffraction
• Diffractive Hard Scattering with a Coherent Pomeron
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• Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
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Cited by in corpus (38)

• The Physics of Ultraperipheral Collisions at the LHC
• Proof of Factorization for Diffractive Hard Scattering
• HERA Collider Physics
• Observation of Diffractive W Boson Production at the Tevatron
• Rapidity Gaps between Jets in Photoproduction at HERA
• Diffractive Production of Jets and Weak Bosons, and Tests of Hard-Scattering Factorization
• Diffractive deeply inelastic scattering of hadronic states with small transverse size
• Measurement of the open-charm contribution to the diffractive proton structure function
• Extra Spin Asymmetries From the Breakdown of TMD-Factorization in Hadron-Hadron Collisions
• Hard scattering factorization and light cone hamiltonian approach to diffractive processes
• Leading twist coherent diffraction on nuclei in deep inelastic scattering at small x and nuclear shadowing
• Double Pomeron Jet Cross Sections
• Measurement of the Diffractive Cross Section in Deep Inelastic Scattering
• Strangeness Production in Deep-Inelastic Positron-Proton Scattering at HERA
• Measurements of Single Diffraction at sqrt(s) = 630 GeV; Evidence for a Non-Linear alpha(t) of the Pomeron
• Review of High Energy Diffraction in Real and Virtual Photon Proton scattering at HERA
• Diffractive Dijet Production at sqrt(s)=630 and 1800 GeV at the Fermilab Tevatron
• Evidence for xi- and t-dependent damping of the Pomeron Flux in the proton
• Estimating Diffractive Higgs Boson Production at LHC from HERA Data
• The H1 Forward Proton Spectrometer at HERA
• Measurement of diffractive production of D*+-(2010) mesons in deep inelastic scattering at HERA
• Three-jet production in diffractive deep inelastic scattering at HERA
• Diffractive J/psi production as a probe of the gluon component in the Pomeron
• The BFKL Pomeron: Can it be Detected?
• Glueball Production in Peripheral Heavy-Ion Collisions
• Associated jpsi + gamma diffractive production: the nature of Pomeron and test of hard diffractive factorization
• Systematics of Leading Particle Production
• Deep Inelastic Scattering at HERA
• Diffractive Mass Spectra at DESY-HERA in the Interacting Gluon Model
• The compatibility of diffractive hard scattering in p pbar and ep collisions
• Diffractive Photoproduction in the Framework of Fracture Functions
• Diffraction at HERA: experimental perspective
• Non-Linear Pomeron Trajectory in Diffractive Deep Inelastic Scattering
• Pomerons and Jet Events at HERA
• Event Shape Analysis of Deep Inelastic Scattering Events with a Large Rapidity Gap at HERA
• Extracting the Pomeron-Pomeron Cross Section from Diffractive Mass Spectra
• Photon Contribution to the ``Super-hard" Pomeron
• Diffraction at HERA - An Experimentalist's View