Metastable exotic multihypernuclear objects

Relativistic heavy ion collisions constitute a prolific source of hyperons: tens of hyperons per event are predicted at energies E≥10 GeV/nucleon, providing a scenario for the formation of metastable exotic multihypernuclear objects. They may exhibit exceptional properties: bound neutral (e.g., 4M2Λ2n, 10M2Λ8n, pure Λ droplets, 8Λ) and even negatively charged composites objects with positive baryon number (e.g., 4M2Σ-2n, 6M2Λ2Ξ-2n) could be formed in rare events. Such negative nuclei can easily be identified in a magnetic spectrometer. They could be considerably more abundant than antinuclei of the same A. We use the relativistic meson-baryon field theory—which gives an excellent description of normal nuclear and single-Λ hypernuclear properties—to calculate the rich spectrum of such exotic objects, their stability, and their structure. We also find solutions for a large variety of bound short-lived nuclei (e.g., 8M2Λ,2Σ-2p2n), which may decay strongly via formation of cascade (Ξ) particles. Multi-Ξ hypernuclei are also evaluated. A variety of potential candidates for such metastable exotic nuclei is presented. It turns out that the properties of such exotic multihypernuclear objects reveal quite similar features as the strangelet proposed as a unique signature for quark-gluon plasma formation in heavy ion collisions

Extraction and low energy transport of negative ions

High perveance negative ion beams with low emittance are essential for several next generation particle accelerators (i. g. spallation sources like ESS [1] and SNS [2]). The extraction and transport of these beams have intrinsic difficulties different from positive ion beams. Limitation of beam current and emittance growth have to be avoided. To fulfill the requirements of those projects a detailed knowledge of the physics of beam formation the interaction of the H- with the residual gas and transport is substantial. A compact cesium free H- volume source delivering a low energy high perveance beam (6.5 keV, 2.3 mA, perveance K= 0.0034) has been built to study the fundamental physics of beam transport and will be integrated into the existing LEBT section in the near future. First measurements of the interaction between the ion beam and the residual gas will be presented together with the experimental set up and preliminary results

Über dich, mich und "Nimby" : Frankfurter Kulturanthropologe beleuchtet Mentalitäten und Lebensstile des Kleinbürgers

Rezension zu: Heinz Schilling : Kleinbürger. Mentalität und Lebensstil ; Verlag Campus, Frankfurt, 2003, ISBN 3-593-37250-9, 252 Seiten, 24,90 Euro

Detectability of strange matter in heavy ion experiments

We discuss the properties of two distinct forms of hypothetical strange matter, small lumps of strange quark matter (strangelets) and of hyperon matter (metastable exotic multihypernuclear objects: MEMOs), with special empha- sis on their relevance for present and future heavy ion experiments. The masses of small strangelets up to AB = 40 are calculated using the MIT bag model with shell mode filling for various bag parameters. The strangelets are checked for possible strong and weak hadronic decays, also taking into account multiple hadron decays. It is found that strangelets which are stable against strong decay are most likely highly negative charged, contrary to previous findings. Strangelets can be stable against weak hadronic decay but their masses and charges are still rather high. This has serious impact on the present high sensitivity searches in heavy ion experiments at the AGS and CERN facilities. On the other hand, highly charged MEMOs are predicted on the basis of an extended relativistic mean field model. Those objects could be detected in future experiments searching for short lived, rare composites. It is demonstrated that future experiments can be sensitive to a much wider variety of strangelets

Hyperstars: phase transition to (meta)-stable hyperonic matter in neutron stars

Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars is investigated. We find that the equation of state exhibits a second stable minimum at large hyperon contents which is in accord with existing hypernuclear data. This second solution gives rise to new effects for neutron star properties which are similar to the ones proposed for the deconfinement transition to strange quark matter and absolutely stable strange stars. We find that the corresponding hyperstars can have rather small radii of R=6-8 km independent of the mass. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.J

Scanning Auger microscopy as applied to the analysis of highly textured YBaCu3Ox thin films

Scanning Auger electron spectroscopy and scanning electron microscopy have been used to investigate the local composition and structure of highly textured axis oriented YBaCuO films with thicknesses in the range 0.4–1 μm. The cuprate films were sputtered on MgO and sapphire (100)-oriented single-crystal substrates at room temperature followed by several anneal stages below or at 920°C in pure oxygen. The YBaCuO/sapphire sample was examined again after an additional 750°C air anneal for 24 h. By applying Auger line profiling on a freshly prepared cross-sectional surface of a thin cuprate film deposited on a sapphire substrate we have been able to show that barium aluminate segregation at grain boundaries is the main cause of the higher electrical resistance usually observed for cuprate films on Al2O3. The (drastic) reduction in Tc can be attributed to the substitution of aluminium in the cuprate at copper sites. Severe interdiffusion has been observed for the epitaxial c axis oriented YBaCu oxide films grown on an MgO substrate, which leads to a deterioration in the superconductivity. The main reason for reduced Tc and quality of cuprate films on MgO is the copper loss into the substrate, the depth of penetration of copper extending more than 400 nm below the YBaCuO---MgO interface. From our experimental results it is evident that Auger line profiling is an important tool in the analysis of high Tc superconducting thin films

Phase transition to hyperon matter in neutron stars

Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R ~ 8 km. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.J

Zur Gültigkeit der Abschreckung im Sinne der ökonomischen Theorie der Kriminalität: Grundzüge einer Meta-Studie

Eine Vielzahl von Forschungsbeiträgen zur Quantifizierung der Präventivwirkung von Strafmaßnahmen haben gemeinsam, diese Abschreckungswirkung im Sinne der ökonomischen Theorie der Kriminalität zumindest einem der Faktoren Strafhöhe und/oder Strafwahrscheinlichkeit zuzusprechen. Inhaltlich zeigen sich jedoch zum Teil starke Abweichungen bei der Berücksichtigung anderer für die Kriminalität entscheidender Einflussgrößen, diese Unterschiede setzen sich in der eingesetzten quantitativen Methodik fort. Es stellt sich die Frage, inwieweit sich Divergenzen in den erzielten Resultaten durch die Heterogenität in den Forschungsansätzen dieser Arbeiten begründen lassen. In diesem Beitrag sollen die Grundzüge einer meta-analytischen Vorgehensweise dargestellt werden, die in der Lage ist, die Resultate unterschiedlicher Forschungsmethoden in einem Ansatz aufzunehmen und systematische Abhängigkeiten zwischen Forschungsdesign und Forschungsergebnis aufzudecken. Die Anwendung der entwickelten Methode zeigt, dass lediglich schwache Zusammenhänge zwischen sowohl inhaltlichen Konzepten als auch technischen Merkmalen und den Resultaten der jeweils verwendeten Forschungsmethode zu finden sind

Phase structure of excited baryonic matter in the relativistic mean field theory

We analyze the phase structure of the nonlinear mean-field meson theory of baryonic matter (nucleons plus delta resonances). Depending on the choice of the coupling constants, we find three physically distinct phase transitions in this theory: a nucleonic liquid-gas transition in the low temperature, Tc2&#961;0 and Tc<50 MeV. All three phase transitions are of first order. It is shown that the occurrence of these different phase transitions depends critically on the coupling constants. Since the production of pions also depends strongly on the coupling constants, it is seen that the equation of state cannot be derived unambiguously from pion data

Influence of space charge fluctuations on the low energy beam transport of high current ion beams

For future high current ion accelerators like SNS, ESS or IFMIF the beam behaviour in low energy beam transport sections is dominated by space charge forces. Therefore space charge fluctuations (e. g. source noise) can drastically influence the beam transport properties of the low energy beam transport section. Losses of beam ions and emittance growth are the most severe problems. For electrostatic transport systems either a LEBT design has to be found which is insensitive to variations of the space charge or the origin of the fluctuations has to be eliminated. For space charge compensated transport as proposed for ESS and IFMIF the situation is different: No major influence on beam transport is expected for fluctuations below a cut-off frequency given by the production rate of the compensation particles. Above this frequency the fluctuations can not be compensated by particle production alone, but redistributions of the compensation particles helps to compensate the influence of the fluctuations. Above a second cut-off frequency given by the density and the temperature of the compensation particles their redistribution is too slow to reduce the influence of the space charge fluctuations. Transport simulations for the IFMIF injector including space charge fluctuations will be presented together with a determination of the cut-off frequencies. The results will be compared with measurements of the rise time of space charge compensation