Experimental Test of Momentum Cooling Model Predictions at COSY and Conclusions for WASA and HESR

The High-Energy Storage Ring (HESR) of the future International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt is planned as an anti-proton cooler ring in the momentum range from 1.5 to 15 GeV/c. An important and challenging feature of the new facility is the combination of highly dense phase space cooled beams with internal targets. A detailed numerical and analytical approach to the Fokker-Planck equation for longitudinal filter cooling including the beam - target interaction has been carried out to demonstrate the stochastic cooling capability. To gain confidence in the model predictions a series of experimental stochastic cooling studies with the internal target ANKE at COSY have been carried out. A remarkable agreement between model and experiment was achieved. On this basis longitudinal stochastic cooling simulations were performed to predict the possibilities and limits of cooling when the newly installed WASA Pellet-target is operated.Comment: 17 pages, 11 figures, Talk given at Symposium on Meson Physics at COSY-11 and WASA-at-COSY, Cracow, Poland, 17-22 Jun 200

THREE-DIMENSIONAL WATER NETWORKS SOLVATING AN EXCESS POSITIVE CHARGE: NEW INSIGHTS INTO THE MOLECULAR PHYSICS OF ION HYDRATION

In a recent effort our group investigated the vibrational mechanics of water using the cage of 20 water molecules surrounding an alkali ion as a paradigm system. The M$^{+}$(H$_{2}$O)$_{20}$ clusters are well known �magic number� species (for the larger alkali metals) and are thought to form a pentagonal dodecahedral web encapsulating the ion. We are attracted to these systems because they are sufficiently large to display broad OH fundamental envelopes in a manner similar to that found in bulk water, but do so with a relatively small number of structurally distinct, three coordinated sites in a finite assembly that, although challenging, can be analyzed with electronic structure calculations in the context of a �supermolecule�. We show how this arrangement can provide an ideal platform on which to unambiguously identify the spectral signatures of particular binding sites, information that is invoked to explain the bulk (and interface) spectrum of water but cannot be directly measured in bulk water.\ Although this behavior is most relevant to simulations of interfacial water, a future direction of this study will be gaining site-specific information for water in an extended two dimensional structure, and the elucidation of the paths of spectral diffusion associated with this arrangement. This unprecedented work will clarify a number of open questions regarding the site-specificity of ground and vibrationally excited state dynamics

THREE-DIMENSIONAL WATER NETWORKS SOLVATING AN EXCESS POSITIVE CHARGE: NEW INSIGHTS INTO THE MOLECULAR PHYSICS OF ION HYDRATION

In a recent effort our group investigated the vibrational mechanics of water using the cage of 20 water molecules surrounding an alkali ion as a paradigm system. The M$^{+}$(H$_{2}$O)$_{20}$ clusters are well known �magic number� species (for the larger alkali metals) and are thought to form a pentagonal dodecahedral web encapsulating the ion. We are attracted to these systems because they are sufficiently large to display broad OH fundamental envelopes in a manner similar to that found in bulk water, but do so with a relatively small number of structurally distinct, three coordinated sites in a finite assembly that, although challenging, can be analyzed with electronic structure calculations in the context of a �supermolecule�. We show how this arrangement can provide an ideal platform on which to unambiguously identify the spectral signatures of particular binding sites, information that is invoked to explain the bulk (and interface) spectrum of water but cannot be directly measured in bulk water.\ Although this behavior is most relevant to simulations of interfacial water, a future direction of this study will be gaining site-specific information for water in an extended two dimensional structure, and the elucidation of the paths of spectral diffusion associated with this arrangement. This unprecedented work will clarify a number of open questions regarding the site-specificity of ground and vibrationally excited state dynamics

Experimental results on strangeness production in proton-proton collisions at COSY

The production of K+ and K- mesons in elementary proton-proton collision has been investigated at the Cooler Synchrotron COSY in Juelich. A high quality proton beam with low emittance and small momentum spread permitted to study the creation of these mesons very close to the kinematical threshold. The energy dependence of the total cross section is investigated using internal beam facilities providing a high accuracy particle momentum determination as well as an external non-magnetic detection setup with a large geometrical acceptance. The determination of the four-momentum vectors for all ejectiles of each registered event gives the complete kinematical information allowing to study the interaction of the outgoing particles. Results on the performed studies of the pp --> pp K+ K-, pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions will be presented and their relevance to the interpretation of heavy ion collisions will be discussed.Comment: 8 pages, 6 figures, plenary talk at 6th International Conference On Strange Quarks in Matter: '2001 - A Flavorspace Odyssey' (SQM2001), Frankfurt, Germany, September 25-29, 2001, to be published in J. Phys. G: Nucl. Part. Phy

Associated strangeness production at threshold

The associated strangeness dissociation at threshold has been studied at the COSY-11 facility measuring the hyperon - and the K+K- meson pair production. Measurements of the near threshold Lambda and Sigma0 production via the pp -> pK+ Lambda / Sigma0 reaction at COSY-11 have shown that the Lambda / Sigma0 cross section ratio exceeds the value at high excess energies (Q >= 300 MeV) by an order of magnitude. For a better understanding additional data have been taken between 13 MeV and 60 MeV excess energy. The near threshold production of the charged kaon-antikaon pair is related to the discussion about the nature of the scalar states in the 1 GeV/c^2 mass range, i.e. the f0(980) and a0(980). The interpretation as a K anti-K molecule is strongly dependent on the K anti-K interaction which can be studied via the production channel. A first total cross section value on the reaction pp -> ppK+K- at an excess energy of 17 MeV i.e. below the phi production threshold was measured.Comment: 3 pages, 2 figures, Presented at Conference on Quarks and Nuclear Physics (QNP 2002), Julich, Germany, 9-14 Jun 200

Organic–Inorganic Surface Modifications for Titanium Implant Surfaces

This paper reviews current physicochemical and biochemical coating techniques that are investigated to enhance bone regeneration at the interface of titanium implant materials. By applying coatings onto titanium surfaces that mimic the organic and inorganic components of living bone tissue, a physiological transition between the non-physiological titanium surface and surrounding bone tissue can be established. In this way, the coated titanium implants stimulate bone formation from the implant surface, thereby enhancing early and strong fixation of bone-substituting implants. As such, a continuous transition from bone tissue to implant surface is induced. This review presents an overview of various techniques that can be used to this end, and that are inspired by either inorganic (calcium phosphate) or organic (extracellular matrix components, growth factors, enzymes, etc.) components of natural bone tissue. The combination, however, of both organic and inorganic constituents is expected to result into truly bone-resembling coatings, and as such to a new generation of surface-modified titanium implants with improved functionality and biological efficacy

Childhood sleep disturbance and risk of psychotic experiences at 18 : UK birth cohort

BACKGROUND: Sleep disturbances are commonly reported in the psychosis prodrome, but rarely explored in relation to psychotic experiences. AIMS: To investigate the relationship between specific parasomnias (nightmares, night terrors and sleepwalking) in childhood and later adolescent psychotic experiences. METHOD: The sample comprised 4720 individuals from a UK birth cohort. Mothers reported on children's experience of regular nightmares at several time points between 2 and 9 years. Experience of nightmares, night terrors and sleepwalking was assessed using a semi-structured interview at age 12. Psychotic experiences were assessed at ages 12 and 18 using a semi-structured clinical interview. RESULTS: There was a significant association between the presence of nightmares at 12 and psychotic experiences at 18 when adjusted for possible confounders and psychotic experiences at 12 (OR = 1.62, 95% CI 1.19-2.20). The odds ratios were larger for those who reported persistent psychotic experiences. CONCLUSIONS: The presence of nightmares might be an early risk indicator for psychosis

Determination of the eta'-proton scattering length in free space

Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton-beam of the Cooler Synchrotron COSY we determine the excitation function for the pp --> pp eta' reaction close-to-threshold. Combining these data with previous results we extract the scattering length for the eta'-proton potential in free space to be Re(a_{p eta'}) = 0+-0.43 fm and Im(a_{p eta'}) = 0.37(+0.40)(-0.16) fm.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let

Hadronic interaction of eta and eta-prime mesons with nucleons

Due to their short life-time, flavour-neutral mesons cannot be utilized as free secondary beams or targets, and therefore a study of their interaction with nucleons is not possible via direct scattering experiments. This interaction is, however, accessible via its influence on the energy dependence - and on the phase space distributions of the cross sections for reactions in which these mesons are produced. In case of the p p --> p p eta reaction the experimentally determined distributions of the differential cross sections close to the production threshold cannot be described by taking into account the S-wave proton-proton and proton-eta interaction only. Here we show that the angular distributions determined at the COSY-11 facility reveal some evidence for P-wave admixture in the proton-proton subsystem already at an excess energy as low as Q = 15.5 MeV. We also present that one can estimate the relative strength of the eta-nucleon and eta-prime-nucleon interactions by comparison of the eta and eta-prime production yield.Comment: 4 pages, 3 figures, Talk given at 16th International Conference on Particles and Nuclei (PANIC 02), Osaka, Japan, 30 Sep - 4 Oct 200

Experimental study of the eta-meson interaction with two-nucleons

By means of the COSY-11 detection system, using a stochastically cooled proton beam of the cooler synchrotron COSY and a hydrogen cluster target, we have performed a high statistics measurement of the pp --> pp eta reaction at an excess energy of Q = 15.5 MeV. The experiment was based on the four-momentum determination of both outgoing protons. This permits to identify pp --> pp eta events and to derive the complete kinematical information of the eta-p-p-system allowing for subsequent investigations of the eta-p interaction. The observed spectrum of the invariant mass of the proton-proton system deviates strongly from the phase-space distribution revealing the influence of the final-state-interaction among the outgoing particles or nontrivial features of the primary production mechanism.Comment: 6 pages, 4 figures, Talk presented at Meson 2002, 7th International Workshop on Meson Production, Properties and Interaction, Cracow, Poland, 24-28 May 200