相关论文: The Transverse Cross Section in Exclusive Vector-M…
We study ways of implementing Fermi momentum in elastic vector-meson production, and find that the usual on-shell assumption of quark models and quark wave functions cannot reproduce the ratio of the longitudinal cross section to the…
Inelastic and elastic (exclusive) cross section measurements of vector meson production at HERA are discussed.
A successful interpretation of the cross sections for elastic and inelastic vector meson production can be made if one assumes the underlying dynamics to be governed by hard partonic subprocesses. Extending these partonic approaches to…
It is shown that the universality of the initial and final state interactions responsible for the transition between the on-- and off--mass shell states leads to the energy independence of the ratio of exclusive $\rho$ electroproduction…
We show that the lowest-order QCD calculation in a simple model of elastic vector-meson production does reproduce correctly the ratios of cross sections for rho, phi and J/psi, both in photoproduction and in high-Q2 quasi-elastic…
The elastic production of vector mesons at HERA is discussed from the theoretical point of view. We briefly review different models, their successes and shortcomings. Main emphasis is put on recent issues in perturbative QCD calculations.…
We present the leading order unpolarized and polarized cross sections in electroweak semi-inclusive deep inelastic leptoproduction. The azimuthal dependences in the cross section differential in the transverse momentum of the vector boson…
We show that the leading twist contribution to exclusive electroproduction of transversely polarized vector mesons vanishes at all orders in perturbation theory. Therefore one cannot extract information on the quark transversity…
Selected recent results from the H1 and ZEUS experiments are reviewed, illustrating some of the many facets of ``meson physics'' at the HERA ep collider. The results cover exclusive elastic and proton-dissociative diffractive vector meson…
The energy dependence of cross sections is discussed as a way to learn about the dynamics of photon induced interactions at HERA. The question of determining the scale of exclusive electroproduction of vector mesons is addressed.
We develop an off-shell extention of the Regge-eikonal approach which automatically takes into account off-shell unitarity. We argue that exclusive vector-meson production cross-sections measured at HERA can be fairly described with…
The H1 Collaboration at the DESY electron-proton collider HERA has observed, in photoproduction and neutral-current deep-inelastic scattering, an unexpected excess of events with isolated leptons and missing transverse momentum, especially…
Estimates for electroproduction of pseudoscalar mesons at small values of skewness are presented. Cross sections and asymmetries for these processes are calculated within the handbag approach which is based on factorization in hard parton…
Exclusive electroproduction of $\phi$ mesons has been studied in $e^\pm p$ collisions at $\sqrt{s}=318 \gev$ with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb$^{-1}$. The $\gamma^*p$ cross section is presented in the…
We calculate the cross-section for events at HERA where the proton loses only a minute fraction of its initial energy, all of which goes into producing a single pair of transverse jets.
A compilation of H1 and ZEUS cross section measurements for elastic vector meson production is presented as a function of the scale $K^2 = (Q^2+M_V^2)/4$, where Q^2 is the exchanged photon virtuality and M_V is the mass of the vector meson.…
Studies on the structure of the photon are presented by means of the extraction of a leading order effective parton distribution in the photon and measurements of inclusive jet differential cross sections in photoproduction. Measurements of…
Exclusive vector meson production from real and virtual photons is, for the most part, described well by soft pomeron exchange. However, there are some unsolved normalisation problems, and just a hint that an additional contribution from…
The elastic electroproduction of phi mesons is studied at HERA with the H1 detector for photon virtualities 1 < Q^2 < 15 GeV^2 and hadronic centre of mass energies 40 < W < 130 GeV. The Q^2 and t dependences of the cross section are…
The energy dependence of exclusive vector meson (V) production is studied using the ZEUS data. The SU(4) universality of V cross sections in the $Q^2+M_V^2$ scale is tested. The energy dependence of the ratio of the cross sections for V…