General thoughts to the Kaon pair production in the threshold region

Simple--minded thoughts about the cross sections for the reactions pp-->ppK+K- and pp-->ppK0K0 are presented, which certainly do not account for the complex coupled channel problem but rather provide some ideas into the mutual reaction dynamics.Comment: Talk given at 9th International Workshop on Meson Production, Properties and Interaction, Cracow, Poland, 9-13 June 2006. 3 pages, 2 figure

Non-equilibrium emission of complex fragments from p+Au collisions at 2.5 GeV proton beam energy

Energy and angular dependence of double differential cross sections d$^2\sigma$/d$\Omega$dE was measured for reactions induced by 2.5 GeV protons on Au target with isotopic identification of light products (H, He, Li, Be, and B) and with elemental identification of heavier intermediate mass fragments (C, N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction mechanisms give comparable contributions to the cross sections. The intranuclear cascade of nucleon-nucleon collisions followed by evaporation from an equilibrated residuum describes low energy part of the energy distributions whereas another reaction mechanism is responsible for high energy part of the spectra of composite particles. Phenomenological model description of the differential cross sections by isotropic emission from two moving sources led to a very good description of all measured data. Values of the extracted parameters of the emitting sources are compatible with the hypothesis claiming that the high energy particles emerge from pre-equilibrium processes consisting in a breakup of the target into three groups of nucleons; small, fast and hot fireball of $\sim$ 8 nucleons, and two larger, excited prefragments, which emits the light charged particles and intermediate mass fragments. The smaller of them contains $\sim$ 20 nucleons and moves with velocity larger than the CM velocity of the proton projectile and the target. The heavier prefragment behaves similarly as the heavy residuum of the intranuclear cascade of nucleon-nucleon collisions. %The mass and charge dependence of the total production cross %sections was extracted from the above analysis for all observed %reaction products. This dependence follows the power low behavior %(A$^{-\tau}$ or Z$^{-\tau}$)

Eta and eta' mesons production at COSY-11

The low emittance and small momentum spread of the proton and deuteron beams of the Cooler Synchrotron COSY combined with the high mass resolution of the COSY-11 detection system permit to study the creation of mesons in the nucleon-nucleon interaction down to the fraction of MeV with respect to the kinematical threshold. At such small excess energies, the ejectiles possess low relative momenta and are predominantly produced with the relative angular momentum equal to zero. Taking advantage of these conditions we have performed investigations aiming to determine the mechanism of the production of eta and eta' mesons in the collision of hadrons as well as the hadronic interaction of these mesons with nucleons and nuclei. In this proceedings we address the ongoing studies of the spin and isospin dependence for the production of the eta and eta' mesons in free and quasi-free nucleon-nucleon collisions. New results on the spin observables for the vec(p)p --> pp eta reaction, combined with the previously determined total cross section isospin dependence, reveal a statistically significant indication that the excitation of the nucleon to the S11(1535) resonance, the process which intermediates the production of the eta meson in the nucleon-nucleon interactions, is predominantly due to the exchange of the pi meson between the colliding nucleons.Comment: Invited talk at MESON 2006: 9th International Workshop on Meson Production, Properties and Interactions, Cracow, Poland, 9-13 Jun 200

Isospin dependence of the eta prime meson production in nucleon-nucleon collisions

A comparison of the close-to-threshold total cross section for the eta prime production in pp --> pp eta prime and pn --> pn eta prime reactions constitutes a tool to investigate the eta prime meson structure and the reaction mechanism in the channels of isospin I=0 and I=1 and may provide insight into the flavour-singlet (perhaps also into gluonium) content of the eta prime meson. In this contribution we present preliminary results of measurement of the quasi-free production of the eta prime meson in the proton-neutron collisions conducted using the COSY-11 facility.Comment: Presented at 10th International Workshop on Meson Production, Properties and Interaction (MESON 2008), Cracow, Poland, 6 - 10 June 200

Study of the 3He-eta system in d-p collisions at COSY-11

We present preliminary results from dp --> 3He X (X=pi0,eta) measurements near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The 3He ejectiles were registered with the COSY-11 detection setup. The ongoing data analysis should deliver high precision data for the dp --> 3He eta total and differential cross sections for the excess energies in the range from threshold up to 9 MeV. The preliminary excitation function for the reaction dp --> 3He pi0 does not show any structure which could originate from the decay of 3He-eta bound state. We present also a threshold excitation curve for the dp --> 3He X channel. Contrary to corresponding results from SATURNE we see no cusp in the vicinity of the eta threshold.Comment: 8 pages; 5 figures; Talk at Eta05 Workshop on Production and Decay of eta and eta-prime Mesons, Cracow, Poland, 15-18 Sep 2005; Acta Phys. Slovaca, in prin

Production of Eta Mesons in Proton-Proton Collisions Close to Threshold

A brief experimental overview on the close-to-threshold eta meson production in proton-proton interactions is presented and the available observables in measurements with unpolarized and polarized beam and target are discussed.Comment: 4 pages; Presented at Meson 2004: 8th International Workshop on Meson Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004; Submitted to International Journal of Modern Physics

Near threshold eta meson production in dp collisions

Preliminary results of recent measurements of the near threshold eta meson production in the dp-->dp eta reaction are presented. The experiment was performed at the COSY-Juelich accelerator with the use of the COSY-11 detection system. Data were taken for three values of deuteron beam momenta corresponding to excess energies of 3.2, 6.1 and 9.2 MeV. The energy dependence of the total cross section confirms a strong effect of the final state interaction.Comment: Talk given at 9th International Workshop on Meson Production, Properties and Interaction, Cracow, Poland, 9-13 June 2006. 5 pages, 3 figure

Study of the production mechanism of the eta meson by means of analysing power measurements

Information about the production mechanism of the eta meson in proton-proton collisions can be inferred by confronting the experimental studies on the analysing power for the p(pol)p --> pp eta reaction with the theoretical predictions of this observable. Results show that the predictions of pure pseudoscalar- or vector meson exchange model are insufficient to describe the analysing powers.Comment: 4 pages, 4 figures, Presented at MESON 2006: 9th International Workshop on Meson Production, Properties and Interactions, Cracow, Poland, 9-13 Jun 200

Dynamics of the near threshold eta meson production in proton-proton interaction

We present the results of measurements of the analysing power for the p(pol)p --> pp eta reaction at the excess energies of Q=10 and 36 MeV, and interpret these results within the framework of the meson exchange models. The determined values of the analysing power at both excess energies are consistent with zero implying that the eta meson is produced predominantly in s-wave.Comment: 3 pages, 3 figures, Presented at the Workshop on the physics of excited nucleons (NSTAR 2007), 5-8 September 2007, Bonn, German