Related papers: Mass dependence in vector--meson electroproduction
We present a quark model study of the $\omega$ meson photoproduction near threshold. With a limited number of parameters, all the data in history are reproduced. The roles played by the {\it s}- and {\it u}-channel processes (resonance…
We present a review of the latest exclusive diffraction results achieved at HERA, discussing in particular the $W$ and $t$ dependence of the measured cross-sections in both DIS and photo-production regimes.
The photoproduction of $D^{*\pm}$ mesons has been measured with the ZEUS detector at HERA at three different ep centre-of-mass energies, $\sqrt{s}$, of 318, 251 and 225 GeV. For each data set, $D^*$ mesons were required to have transverse…
The exclusive production of vector mesons and photons in $ep$ collisions is investigated considering three phenomenological saturation models based on distinct assumptions for the treatment of the dipole - hadron scattering amplitude. The…
The process of exclusive vector meson production (gamma gamma to J/psi rho^0) is studied for almost real photons. This process may be reduced to photoproduction of J/psi off the rho^0 meson. We discuss the possibility of extracting the…
The suggestion of momentum dependence in the amplitude for rho-omega mixing has generated concern over related implications for vector meson dominance and the photon-rho coupling. We discuss two established representations of vector meson…
A model based on a dipole Pomeron framework for vector meson exclusive photoproduction by real and virtual photons shows very good agreement with the experimental data. The model does not violate unitarity constrains and describes in a…
New results on elastic (exclusive) production of vector mesons are presented, mainly on J/\psi and phi mesons with emphasis on an interpretation of the data within pQCD.
The coherent $\omega$-meson photoproduction from nuclei is proposed as a phenomenological method to evaluate the momentum dependence of $\omega$-meson mass shift and width in nuclear matter. We analyze available data on un-separated…
Diffractive vector meson photoproduction accompanied by proton dissociation is studied for large momentum transfer. The process is described by the non-forward BFKL equation which we use to compare to data collected at the HERA collider.
The structure of real and virtual photons has been studied in ep collisions at HERA using dijet production. Measurements of differential dijet cross sections as function of the fraction of photon's momentum invested in the dijet system are…
By using a Regge-pole model for vector meson production (VMP), successfully describing the HERA data, we analyse the correlation between VMP cross sections in photon-induced reactions at HERA and those in ultra-peripheral collisions at the…
Multiple interaction models satisfying $s$-channel unitarity predict that, in contrast to inelastic processes, factorization is violated in diffractive processes. The size of this effect can be characterized in terms of the rapidity gap…
In a framework for nonperturbative QCD calculation of high energy processes, the amplitudes for photo- and electroproduction of vector mesons are written as integrals of the overlap product of photon and vector meson wave functions,…
We investigate the role of unitarization effects in virtual photon-proton (\gamma^*p) interactions at small x. The q\bar{q}-fluctuation of the initial photon is separated into a small distance and a large distance component and a model for…
We show that lepton-pair production in Virtual Compton Scattering offers, through interference with the well-known Bethe-Heitler process, a sensitive probe to learn the longitudinal response of resonances and the electromagnetic nucleon…
Data for the differential cross sections for $\gamma^* p\to\rho^0 p$, $\gamma^* p \to \phi p$ and $\gamma^* p\to J/\psi p$, at all available values of $Q^2$, fit very well to a combination of soft pomeron, hard pomeron and $f_2$ exchange.
Recent results of particle production in the energy regime of the CERN-SPS are reviewed. In order to collect information on the properties of the QCD phase diagram systematic studies of the system size and the energy dependence of particle…
The photoproduction of $\omega$ and $\eta^\prime$ mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9 GeV at the electron accelerator ELSA. The mesons have been…
Relativistic heavy ions are copious sources of virtual photons. The large photon flux gives rise to a substantial photonuclear interaction probability at impact parameters where no hadronic interactions can occur. Multiple photonuclear…