Related papers: Physics with two photons at HERA
The production of prompt photons is measured in the photoproduction regime of electron-proton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340 pb^-1 collected by the H1…
Data taken at the Pierre Auger Observatory are used to search for air showers initiated by ultra-high energy (UHE) photons. Results of searches are reported from hybrid observations where events are measured with both fluorescence and array…
Future prospects of hard diffraction at HERA a reviewed. A selection of processes which can be calculated in pQCD is given, with emphasis on the separation of soft and hard diffraction. The main focus will be put on the energy dependence of…
This report is a short overview of experimental and theoretical results in J/psi production in electron-proton collisions at DESY HERA with special focus lying on recent developments in inelastic photoproduction.
Ultra-relativistic heavy-ions carry strong electromagnetic and nuclear fields. Interactions between these fields in peripheral nucleus-nucleus collisions can probe many interesting physics topics. This presentation will focus on coherent…
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…
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…
From 1992 to 2007, HERA, the first electron-proton collider, operated at cms energies of about 320 GeV and allowed the investigation of deep-inelastic and photoproduction processes at the highest energy scales accessed thus far. This review…
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.
The production of a single exotic Higgs particle is studied at Hera. Within the present limits on the Yukawa couplings this doubly charged particle, suggested by the left-right symmetric models, can be observed at Hera up to values of its…
In the context of the tremendous progress achieved at HERA in diffraction and the need for a new level of statistical and systematic precision, the new very large acceptance forward spectrometer planned by H1 (VFPS) is presented and the…
We discuss two-photon physics, taking for illustration the particular but topical case of resonance fluorescence. We show that the basic concepts of interferences and correlations provide at the two-photon level an independent and…
A future $ep$ facility, THERA, where electrons of 250 GeV and protons of 920 GeV are collided could provide valuable information on the structure of the photon. With an increase in the centre-of-mass energy of a factor of 3 and an extension…
Some general considerations on a future linear collider and selected topics of two photon physics measurements which can be performed at such a collider are presented. This review discusses the total photon-photon cross section, jet cross…
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.
In this article aspects of photon-photon physics related to the structure of real and virtual photons are reviewed. A re-calculation of the virtual photon-photon box is performed and some discrepancies in the literature are clarified. A…
Collective behaviour of final-state hadrons, and multiparton interactions are studied in high-multiplicity $ep$ scattering at a centre-of-mass energy $\sqrt{s}=318$ GeV with the ZEUS detector at HERA. Two- and four-particle azimuthal…
The high energy photoproduction of jets is being observed at the ep collider, HERA. It may be that the HERA centre-of-mass energy is sufficiently large that the production of more than one pair of jets per ep collision becomes possible,…
Collisions of atomic nuclei at relativistic velocities allow to recreate the conditions encountered in neutron stars or in the early universe micro-seconds after the Big Bang. These reactions are performed in today's largest accelerator…
Data on low x physics from H1 & ZEUS are presented and their interpretation discussed. The focus is on the increasing hardness of the energy dependence of inclusive virtual-photon proton scattering and certain diffractive processes as the…