Related papers: Partonic structure of the virtual photon
We introduce operator definitions for virtual photon fragmentation functions, which are needed for reliable calculations of Drell-Yan transverse momentum ($Q_T$) distributions when $Q_T$ is much larger than the invariant mass $Q$. We derive…
The recent F$_2$ measurements at HERA are discussed in the framework of virtual photon--proton cross section. The energy behaviour of the cross section is studied for different $Q^2$ values, ranging from 0 to 1000 GeV$^2$ for center of mass…
We discuss in detail the photon structure function beyond the leading logarithm approximation. Of special concern is the factorization scheme and the hadronic input; we show how to naturally absorb large terms due to the MSbar factorization…
The contribution of both inclusive and exclusive cross-section data from HERA to our knowledge of parton distribution functions is reviewed and future prospects are outlined.
This report summarizes some of the recent HERA results obtained by studying hard processes in ep-scattering. By resolving the structure of the proton, hard ep-reactions provide information on the parton content of the proton and may give…
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.
We report on the status of the phenomenological access of generalized parton distributions from photon and meson electroproduction off proton. Thereby, we emphasize the role of HERMES data for deeply virtual Compton scattering, which allows…
The parton content of real (P^2=0) and virtual (P^2\neq 0) transverse photons \gamma(P^2) is expressed in terms of perturbative pointlike and nonperturbative hadronic (VMD) components, employing recently updated parton distributions of…
Measurements of jet production in the photoproduction region at HERA are presented, which are sensitive to the underlying event structure. It is argued that in the photoproduction region a significant amount of multi-parton interactions in…
A `complete' framework for gamma-gamma / gamma*-gamma / gamma*-gamma* interactions is presented. The emphasis is on providing a model for gamma-gamma physics at all photon virtualities, including the difficult transition region around the…
In the framework of the vector dominance model (VDM) new contribution into the cross-section of $D^*$-meson photoproduction at HERA has been estimated. This contribution is due to the interaction of the virtual vector $c\bar c$-mesons from…
Twist-2 components of the real and virtual photon distribution amplitudes are evaluated in several chiral quark models. The results, obtained at the quark model scale, are then evolved to higher scales, probed in experiments or in lattice…
We present a comparison of a recently proposed model, which describes the Deeply Virtual Compton Scattering amplitude, to the HERA data.
The three-dimensional structure of nucleons (protons and neutrons) is embedded in so-called generalized parton distributions, which are accessible from deeply virtual Compton scattering. In this process, a high energy electron is scattered…
In peripheral relativistic heavy ion collisions at the Large Hadron Collider, jet+jet and photon+jet final states can be produced when a photon from the virtual photon field surrounding the nucleus interacts with a parton in the opposite…
The large luminosity and the increased kinematical domain accessible at the LHC will allow to isolate large numbers of events with multiple parton collisions. Interestingly, the hadron is probed in different points contemporarily in the…
A significant fraction of pp collisions at the LHC will involve (quasi-real) photon interactions occurring at energies well beyond the electroweak energy scale. Hence, the LHC can to some extend be considered as a high-energy photon-photon…
At $e^+e^-$ and $ep$ colliders, the large fluxes of almost on-shell photons accompanying the lepton beams lead to the photoproduction of jets. As the centre-of-mass energy is increased, regions of smaller $x$ in the parton densities are…
Recent measurements of jet cross sections at HERA, the Tevatron and the LHC that provide constraints on parton distribution functions and allow for determinations of the strong coupling constant are presented.
QCD corrections to the QED formula for parton distribution functions of the longitudinal virtual photon are derived in the leading--logarithmic approximation. It is shown that the resulting PDF satisfy the same homogeneous evolution…