SubthresholdK + production in proton-nucleus collisions

We analyzed theK ⁺ production at projectile energies below the free nucleon-nucleon threshold in proton-nucleus collisions and studied the contribution from different reaction channels to this process. It was shown that the secondary pion-nucleon (+N+K ⁺) channel significantly prevails over the direct (p+N+N+K ⁺) one. The momentum and angularK ⁺ spectra were calculated in the framework of different production channels in order to propose experimental measurements which allow to distinguish the mechanisms discussed. We also studiedK ⁺ d correlations and considered the deuteron reabsorption in the nuclear medium as well as the fast deuteron background. The features ofK ⁺ p correlations related to the different production channels were analyzed as well.     

Antikaon production in nucleon- nucleon reactions near threshold

The antikaon production cross section from nucleon-nucleon reactions near threshold is studied in a meson exchange model. We include both pion and kaon exchange, but neglect the interference between the amplitudes. In case of pion exchange the antikaon production cross section can be expressed in terms of the antikaon production cross section from a pion-nucleon interaction, which we take from the experimental data if available. Otherwise, a K* -resonance exchange model is introduced to relate the different reaction cross sections. In case of kaon exchange the antikaon production cross section is related to the elastic KN and K?N cross sections, which are again taken from experimental measurements. We find that the one-meson exchange model gives a satisfactory fit to the available data for the NN → NN KK? cross section at high energies. We compare our predictions for the cross section near threshold with an earlier empirical parameterization and that from phase space models.     

Primakoff effect in $ \eta$ -photoproduction off protons

We analyse data on forward h \eta -meson photoproduction off a proton target and extract the h \eta ? \rightarrow g \gamma g \gamma decay width utilizing the Primakoff effect. The hadronic amplitude that enters into our analysis is strongly constrained because it is fixed from a global fit to available g \gamma p ? \rightarrow p h \eta data for differential cross-sections and polarizations. We compare our results with present information on the two-photon h \eta -decay from the literature. We provide predictions for future PrimEx experiments at Jefferson Laboratory in order to motivate further studies.     

Simultaneous separation of actinides and technetium from large volumes of natural water for their determination

Journal of Radioanalytical and Nuclear Chemistry - Monitoring of radionuclide concentration in natural samples is important for assessing environmental safety. The low concentration of long-lived...     

Aspects of φ-meson production in proton-proton collisions

We analyze near-threshold cross-section data for the reaction pp → ppφ published by the DISTO Collaboration and recent, still preliminary results presented by the ANKE Collaboration. We formulate a procedure to evaluate the OZI ratio at low energies by taking into account corrections from the kinematics and the final-state interaction. Combining the new data with the few measurements available at higher energies we give a limit for the OZI rule violation. We also demonstrate and discuss the effect of a possible contribution from a five-quark baryonic resonance coupled to the φp system on the pp → ppφ cross-section and the φp and pp invariant mass spectra.     

Charmed meson rescattering in the reaction $$ \bar pd \uparrow \bar DDN $$

We examine the possibility to extract information about the DN and interactions from the reaction. We utilize the notion that the open-charm mesons are first produced in the annihilation of the antiproton on one nucleon in the deuteron and subsequently rescatter on the other (the spectator) nucleon. The latter process is then exploited for investigating the DN and interactions. We study different methods for isolating the contributions from the D ⁰ p and D ⁻ p rescattering terms.     

a+0 (980)-resonance production in pp-->dK+K-0 reactions close to threshold

The reaction pp-->dK+K(-)0 has been investigated at an excess energy of Q=46 MeV above the K+K(-)0 threshold with ANKE at the cooler synchrotron COSY-Jülich. From the detected coincident dK(+) pairs, about 1000 events with a missing K(-)0 were identified, corresponding to a total cross section of sigma(pp-->dK+K(-)0)=[38+/-2(stat)+/-14(syst)] nb. Invariant-mass and angular distributions have been jointly analyzed and reveal s-wave dominance between the two kaons, accompanied by a p wave between the deuteron and the kaon system. This is interpreted in terms of a(+)0 (980)-resonance production.     

Analysis of recent $ \eta$ photoproduction data

Recent data on h \eta -meson photoproduction off a proton target in the energy range 2￡ \le ?{s} \sqrt{{s}} ￡ \le3 GeV are analyzed with regard to their overall consistency. Results from the ELSA and CLAS measurements are compared with predictions of a Regge model whose reaction amplitude was fixed via a global fit to pre-2000 measurements of differential cross sections and polarization observables for g \gamma p ? \rightarrow h \eta p at higher energies. We find that all recent experimental results on differential cross sections for h \eta -meson photoproduction are in good agreement with each other, except for the CLAS data from 2009. However, the latter can be made consistent with the other data at the expense of introducing an energy-dependent renormalization factor. We point out that there are indications in the data for a possible excitation of baryon resonances with masses around 2.1 and 2.4GeV.     

Width of the ? meson in nuclear matter

The ratios of the cross sections for ?-meson production induced by 2.83-GeV protons on Cu, Ag, and Au nuclei to the respective cross section for C nuclei were measured at the ANKE-COSY facility in the momentum range of 0.6?C1.6 GeV/c and the angular range of 0°?C8°. The product ? mesons were identified by their decay ? ?? K ⁺ K ^?. The procedure used to separate kaon pairs was described in detail, and all sources of the background and their contribution to the resulting error in the values found for the above cross-section ratios were analyzed. The A dependence of the cross section for ?-meson production was shown to obey the A ^0.56±0.03 law. The total width of the ? meson at a normal nuclear density was extracted from a comparison of the measured cross-section ratios with the results of calculations based on two theoretical models. The resulting width value exceeds substantially both the vacuum width and the width expected in the absence of the nuclear-matter effect on the properties of the ? meson.