Related papers: Jets as a Source of Information about Photon Struc…
Two-jet production from the direct photon contribution at HERA is a sensitive measure of the small-$x$ gluon in the proton. We propose measurements of ratios of the jet cross-sections which will clearly distinguish between gluons with or…
Measurements sensitive to the structure of both real and virtual photons are presented and compared to theoretical models with various photon parton distribution functions (PDFs). Measurements for real photons show a tendency for the…
In this article we present a review of the structure of the proton and the current status of our knowledge of the parton distribution functions (PDFs). The lepton-nucleon scattering experiments which provide the main constraints in PDF…
The latest results on the structure of the proton and the photon as seen at HERA are reviewed while discussing the question posed in the title of the talk.
Starting in 2008 the H1 and ZEUS experiments have been combining their data in order to provide the most complete and accurate set of deep-inelastic data as the legacy of HERA. The present review presents these combinations, both published…
In this talk I first briefly explain the puzzle presented by the high muon content observed in air-showers which point to the ultra high-energy $\gamma$ sources like the HER-X-1. Since it had been suggested that a possible explanation of…
The double-differential inclusive di-jet cross section in photoproduction processes is measured with the H1 detector at HERA. The cross section is determined as a function of the average transverse jet energy E_T^jets for ranges of the…
A survey is presented of the various processes measurable at HERA in which two photons are involved. Their current experimental status and future prospects are discussed.
Inclusive neutral and charged current cross sections and structure functions measured at HERA-I are briefly reviewed. The impact of these measurements on parton density functions is discussed. The emphasis is put on the high x region. A…
Photons resulting from jet-medium interactions offer the opportunity of studying the evolving quark distribution in a heavy ion collision. The spectra of jet-medium photons is presented within the JETSCAPE framework for two different energy…
This review covers selected results from the LEP experiments on the structure of quasi-real and virtual photons. The topics discussed are the total hadronic cross-section for photon-photon scattering, hadron production, jet cross-sections,…
The total hadronic photon-photon cross-section measured by L3 and OPAL and the apparent discrepancy between the results are discussed. OPAL measurements of jet and charged hadron production in photon-photon scattering and preliminary H1…
The measurements of hadronic structure functions of the photon based on the reaction ee --> ee gamma^(*)(P^2) gamma^*(Q^2)--> ee hadrons are discussed.
The status of the measurements and the theoretical developments concerning the hadronic structure of the photon are briefly summarised.
The sensitivity of the Deep Inelastic Compton (DIC) scattering at HERA to the structure of the virtual photon is discussed. It is demonstrated that the gluonic content of the virtual photon can be pinned down by measuring the photons with…
A pedagogical introduction to the experimental results on hard photoproduction at HERA is provided. Then the latest results in this field from ZEUS and H1 are reviewed.
The production of final state photons in deep inelastic scattering originates from photon radiation off leptons or quarks involved in the scattering process. Photon radiation off quarks involves a contribution from the quark-to-photon…
The basic concepts and predictions of the `dynamical' GRV parton distributions for hadrons and photons are discussed. Comparisons of these predictions with recent experimental results, especially from HERA, are presented.
Recent results on jet cross sections and heavy-flavor production in photoproduction and neutral current deep inelastic ep scattering from the H1 and ZEUS Collaborations are presented. The jet measurements are used to perform stringent tests…
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…