η′\eta^{\prime} Production in Proton-Proton Collisions near Threshold

Within the one-pion exchange model we calculate the near-threshold ${\eta}^{\prime}$ production from $pp$ collisions including the final state interaction between the protons. Since the description of the data is quite well we conclude that $\eta, \rho$ or $\omega$ exchange currents either play no role or cancel each other to a large extent in this reaction.Comment: 7 pages, LaTeX, including 3 ps-figures, UGI-98-20. To be pub. EPJ-

On the current status of OZI violation in πN{\pi}N and pp reactions

The available data on $\omega$ and $\phi$ production from $\pi N$ and $pp$ collisions are reanalyzed with respect to an OZI rule violation on the basis of transition matrix elements. The data are found to be compatible with a constant ratio $R$ up to excess energies $\epsilon{\approx}300$ MeV, however, the ratio $R$ deviates substantially from the SU(3) prediction based on the present knowledge of the $\phi-\omega$ mixing angle.Comment: 6 pages, svjour-style, including 10 ps-figure

Incoherent Eta Photoproduction from the Deuteron near Threshold

Very recent data for the reaction gamma+d ->eta np, namely total cross sections, angular and momentum spectra, are analyzed within a model that includes contributions from the impulse approximation and next order corrections due to the np and eta-N interactions in the final state. Comparison between the calculations and the new data indicate sizable contributions from the np and eta-N final state interactions. Some systematic discrepancies between the calculations and the data are also found

Studying the ω\omega properties in pA collisions via the ω→π0γ\omega{\to}\pi^0\gamma decay

Within transport calculations we study the production and decay of $\omega$-mesons in $pA$ reactions at COSY energies including elastic and inelastic ${\omega}N$ rescattering, the $\omega{\to}\pi^0\gamma$ Dalitz decay as well as $\pi^0 N$ rescattering. The resulting invariant $\pi^0 \gamma$ mass distributions indicate that in-medium modifications of the $\omega$-meson may be observed experimentally.Comment: 5 pages, espcrc2-style, including 5 ps-figure