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Within the meson exchange model we study $omega$ meson photoproduction at energies above the s channel resonance region. Different model prescriptions for the $omega{NN}$ vertex function are investigated imposing gauge invariance as well as crossing symmetry. The calculations reproduce the energy dependence of the differential $omega$ photoproduction cross sections at moderate $|u|$ for $E_gamma{le}4.7$ GeV, which previously were discussed as an indication of the hard interaction between the photon and quarks of the nucleon.
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Photoproduction of omega-meson is analyzed within meson exchange model and Regge model and compared to rho-meson photoproduction. An interplay between two models and uncertainties in data reproduction are discussed.
Cross-sections and recoil polarizations for the reactions gamma + p --> K^+ + Lambda and gamma + p --> K^+ + Sigma^0 have been measured with high statistics and with good angular coverage for center-of-mass energies between 1.6 and 2.3 GeV. In the K^+Lambda channel we confirm a structure near W=1.9 GeV at backward kaon angles, but our data shows a more complex s- and u- channel resonance structure than previously seen. This structure is present at forward and backward angles but not central angles, and its position and width change with angle, indicating that more than one resonance is playing a role. Rising back-angle cross sections at higher energies and large positive polarization at backward angles are consistent with sizable s- or u-channel contributions. None of the model calculations we present can consistently explain these aspects of the data.
We present a unified relativistic approach to inclusive electron scattering based on the relativistic Fermi gas model and on a phenomenological extension of it which accounts for the superscaling behaviour of $(e,e)$ data. We present results in the $Delta$ resonance region and in the highly inelastic domain and show some application to neutrino scattering.
Systematic analysis of available data for $omega$-meson photoproduction is given in frame of Regge theory. At photon energies above 20 GeV the $gamma{+}p{to}omega{+}p$ reaction is entirely dominated by Pomeron exchange. However, it was found that Pomeron exchange model can not reproduce the $gamma{+}p{to}rho{+}p$ and $gamma{+}p{to}omega{+}p$ data at high energies simultaneously with the same set of parameters. The comparison between $rho$ and $omega$ data indicates a large room for meson exchange contribution to $omega$-meson photoproduction at low energies. It was found that at low energies the dominant contribution comes from $pi$ and $f_2$-meson exchanges. There is smooth transition between the meson exchange model at low energies and Regge theory at high energies.
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 reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasi-free protons bound in the deuteron to the results for free protons and then applied as a correction to the quasi-free neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between $0.45$~GeV and $1.4$~GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.
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