Related papers: Real and Virtual Photon Structure
New measurements of dijet photoproduction at HERA provide information on the gluon density in the photon and on its quark densities at high x_gamma and high factorisation scales.
The electron-proton collider HERA at DESY opened the door for the study of diffraction in real and virtual photon-proton scattering at center-of-mass energies W up to 250 GeV and for large negative mass squared -Q^2 of the virtual photon up…
Recent experimental results on the partonic structure of the photon and on the color singlet exchange in strong interaction processes are reviewed. At the LEP electron-positron and HERA lepton-proton colliders, complementary and consistent…
The virtual photon structure function $g_1^{\gamma}(x,Q^2,P^2)$, which can be obtained in polarized $e^{+}e^{-}$ colliding-beam experiments, is investigated for $\Lambda^2 \ll P^2 \ll Q^2$, where $-Q^2$ ($-P^2$) is the mass squared of the…
The dependence of the photon structure on the photon virtuality, Q^2, is studied by measuring the reaction e^+p\to e^+ + {\rm jet} + {\rm jet} + {\rm X} at photon-proton centre-of-mass energies 134 < W < 223 GeV. Events have been selected…
Present data on the partonic content of the photon are reviewed. The results on the unpolarized structure functions from DIS experiments and on large pt jet production processes in gamma-gamma and gamma-p collisions are discussed for both…
The cross section for photoproduction of an isolated prompt photon in association with a jet is studied in Next-to-Leading Order. The kinematics are those appropriate for the DESY $ep$ collider HERA. The effects on the cross section of…
We demonstrate that a future high-energy electron-proton collider like THERA could largely extend the current HERA program in jet photoproduction of testing QCD and determining the partonic structure of the proton and the photon. Depending…
We present a next-to-leading order calculation of jet production in gamma^*gamma collisions from e+e- scattering in a region where the virtuality Q^2 of the probing virtual photon is small compared to the transverse jet energy. The…
The amplitudes for virtual Compton scattering off protons are calculated within the framework of the diquark model in which protons are viewed as being built up by quarks and diquarks. The latter objects are treated as quasi-elementary…
The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS…
In this work, we provide a comprehensive set of differential cross-section distributions for photon + di-jet production in proton-proton collisions with next-to-next-to-leading order precision in massless QCD. The event selection…
The Deeply Virtual Compton Scattering (DVCS) $\gamma^* p \to \gamma p$ cross section has been measured with the H1 detector at HERA with an increased precision and in an extended kinematic domain: at photon virtualities $4<Q^2<80$ GeV$^2$,…
The QCD treatment of the photon structure is recalled. Emphasis is given to the recently derived momentum sum rule, and to the proper choice of the factorization scheme and/or boundary conditions for the evolution equations beyond the…
Recent results on diffraction at HERA, as measured by the H1 and ZEUS collaborations, are reviewed. Results on the photon-proton total hadronic cross section, on vector meson production both at small and large photon virtuality and on…
We discuss forward jet production data recently published by the H1 and ZEUS collaborations at HERA. We review how several Monte-Carlo models compare to the data. QCD calculations based on the BFKL formalism and on fixed NLO perturbation…
Over the last two decades, the HERA collider has provided a large amount of new information about QCD dynamics at high energy. While the most appreciated are the measurements of the proton structure functions in a wide range of parton…
Dijet production by almost real photons has been studied at HERA with the ZEUS detector. Jets have been identified using the cone algorithm. A cut on xg, the fraction of the photon energy participating in the production of the two jets of…
The present theoretical knowledge about photons and hard photoproduction processes, i.e. the production of jets, light and heavy hadrons, quarkonia, and prompt photons in photon-photon and photon-hadron collisions, is reviewed. Virtual and…
We review several most recent prompt-photon measurements at HERA and the Tevatron and discuss their implication for future measurements at the LHC. A comparison to Monte Carlo models, as well as to NLO QCD predictions based on the standard…