Search

Within the spectator model, we study the reaction γ d → K −Θ+ p → K − K + np in the threshold energy region. We present the predictions for the exclusive and inclusive K −-meson angular distributions in the laboratory system for this reaction calculated for two possible parity states of the Θ+ resonance at 1.5-and 1.75-GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the sampled phase space where the contribution from the main background sources, associated with the ϕ(1020), Λ(1520) production as well as with the K − p rescattering in the final state, is expected to be dominant. We show that, under the chosen kinematics, these distributions are sensitive to the Θ+ parity and, therefore, can be used as a filter for the determination of its parity. [ABSTRACT FROM AUTHOR]

The production of non-ϕK+K− pairs by protons at 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets has been investigated by using the COSY-ANKE magnetic spectrometer. The K− momentum dependence of the differential cross section has been measured for laboratory polar angles θK± ≤ 12∘ over the 0.2-0.9 GeV/c range. The comparison of the data with detailed model calculations indicates an attractive K−-nucleus potential of about −60 MeV at normal nuclear matter density at a mean momentum of 0.5 GeV/c. However, this approach has difficulty in reproducing the smallness of the observed cross sections at low-K− momenta. [ABSTRACT FROM AUTHOR]

Inclusive cross sections σA = Ed3α(X, P21)/d3p of antiproton and negative pion production on Be, Al, Cu, and Ta targets hit by 10-GeV protons were measured at the laboratory angles of 10.5° and 59°. Antiproton cross sections were obtained in both kinematically allowed and kinematically forbidden regions for antiproton production on a free nucléon. The antiproton cross-section ratio as a function of the longitudinal variable X exhibits three separate plateaus, which gives evidence for the existence of compact baryon configurations in nuclei--small-distance scaled objects of nuclear structure. The comparability of the measured cross-section ratios with those obtained in the inclusive electron scattering off nuclei suggests weak antiproton absorption in nuclei. Observed behavior of the cross-section ratios is interpreted in the framework of a model considering the hadron production as a fragmentation of quarks (antiquarks) into hadrons. It has been established that the antiproton formation length in nuclear matter can reach the magnitude of 4.5 fm. [ABSTRACT FROM AUTHOR]