Related papers: Unitarity constraints on meson electroproduction a…
The background due to the direct diffractive dissociation of the photon into the $\pi^+\pi^-$-pair to the "elastic" diffractive $\rho^0$-meson production in electron-proton collisions is calculated. At large $Q^2$ the interference between…
We investigate the exclusive electroproduction of pi^+ mesons from nucleons. To leading twist, leading order alpha_s accuracy the corresponding production amplitude can be decomposed into pseudovector and pseudoscalar parts. Both can be…
Photoproduction of pi0 mesons was studied with the Crystal-Barrel detector at ELSA for incident energies from 300 MeV to 3 GeV. Differential cross sections d sigma /d Omega, d sigma/d t, and the total cross section are presented. For…
Precise angular distributions have been measured for the first time for the photoproduction of $\pi^{0}$-mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic…
Photoproduction cross sections are reported for the reaction $\gamma p\to p\eta$ using energy-tagged photons and the CLAS spectrometer at Jefferson Laboratory. The $\eta$ mesons are detected in their dominant charged decay mode, $\eta\to…
Odderon induced contributions to exclusive photoproduction of $\pi^{\circ}$, $f_2(1270)$ and $a_2(1320)$ have been searched for at HERA, using the multiphoton decays of these mesons. No indication for such contributions was found, in a…
Assuming the proton's light-cone wave function to be dominated by small parton virtualities and small intrinsic transverse momenta, we show that the electroproduction amplitudes at large momentum transfer factorize into parton-level…
The exclusive reaction $\gamma p \to p \pi^+ \pi^-$ was studied in the photon energy range 3.0 - 3.8 GeV and momentum transfer range $0.4<-t<1.0$ GeV$^2$. Data were collected with the CLAS detector at the Thomas Jefferson National…
For complete development of quantum electrodynamics in the presence of a strong external field, the proper understanding of resonant processes and all their peculiarities is essential. We present our attempt to analytically investigate the…
We calculate the cross section of diffractive charge-parity C=+1 neutral meson production in virtual photon proton collision at high energies. Due to the opposite C-parities of photon and meson M (M = eta_C, pi^0, a_2) this process probes…
Hard diffractive photo- and electroproduction of heavy vector mesons ($J/\psi$ and $\Upsilon$) is evaluated within the leading $\alpha_s\ln{Q^2 \over\Lambda_{QCD}^2}$ approximation of QCD. In difference from our earlier work on that…
The amplitude for hard exclusive pseudoscalar meson electroproduction off nucleon (nuclear) targets is computed in QCD within the leading $\alpha_s \ln {Q^2/\lambda_{QCD}^{2}}$ approximation. We show that the distribution of recoil nucleons…
We report the first measurement at the LHC of coherent photoproduction of $\rho^0$ mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for $\rho^0$ production are studied in the $\pi^+…
We analyze electroproduction of light vector mesons (V=rho, phi and omega) at small Bjorken-x in the handbag approach in which the process factorizes into general parton distributions and partonic subprocesses. The latter are calculated in…
The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were…
The $e p\to e^\prime p \rho^0$ reaction has been measured, using the 5.754 GeV electron beam of Jefferson Lab and the CLAS detector. This represents the largest ever set of data for this reaction in the valence region. Integrated and…
An investigation of $\gamma p\to \omega p$ is presented in a constituent quark model approach. The sparse data in the large $t$ region where the resonances dominate is well described within the model, while the diffractive behavior in the…
We show that photoproduction cross sections recently measured by ZEUS and H-1 at HERA energies$^1$ are in agreement with our earlier prediction based on high-energy hadronic structure of the photon in the QCD minijet-type model$^2$. We…
We discuss various aspects of vector meson production, first analysing the interplay between perturbative and nonperturbative aspects of the QCD calculation. Using a general method adapted to incorporate both perturbative and nonpertubative…
We study photoproduction of rho mesons in a model of hidden local symmetry. The rho meson is introduced as a hidden gauge boson and a phenomenological rho meson-nucleon Lagrangian is constructed respecting chiral symmetry. It is shown that…