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Study of the energy flow in sulphur-and oxygen-nucleus collisions at 60 and 200 GeV/nucleon

Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.     

Dielectric properties and the ferroelectric transition of the Stockmayer-fluid via computer simulation

We report extensive molecular dynamics simulations of the Stockmayer fluid near the transition to fluid ferroelectric ordering monitored via the divergence of the static dielectric constant. The dependence of the transition on dipole strength, μ², temperature, T, and system size is investigated. The results are compared to a large number of previous simulations in the literature. We find that the effective transition temperature T/(ρ μ²) ≈ 0.19 for ρ?=?0.8 is a good estimate in the range of the other parameter values considered here. In addition, we study the local field in relation to the structure and dynamics of the liquid phase as a function of temperature, dipole strength and polarizability.     

Small-angle correlations of identical particles in carbon-carbon interactions atP=4.2 GeV/c per nucleon

Two-particle small-angle correlations between negative pions and between protons in carbon-carbon collisions atP=4.2 GeV/c per nucleon have been studied, both for an unbiased sample and for “central” events. A comparison of experimental π^? π^? andpp correlation functions with theoretical predictions has been made. A possible evidence for the existence of two fireballs in C+C interactions atP=4.2 GeV/c per nucleon is presented.     

Size of the proton emission region inp-C,d-C, α-C and C-C interactions at 4.2 GeV/c per incident nucleon from two-proton correlations

Correlations between secondary protons with small relative momenta have been studied in interactions of various light nuclei with the carbon target at 4.2 GeV/c per incident nucleon with the aim to determine the radius of the proton emission region. This radius is found to decrease with increasing momentum and transverse momentum of the proton pair, but it does not show any dependence on the mass of the projectile nucleus.     

Interface of nanoparticle-coated electropolished stents

Nanostructures entail a high potential for improving implant surfaces, for instance, in stent applications. The electrophoretic deposition of laser-generated colloidal nanoparticles is an appropriate tool for creating large-area nanostructures on surfaces. Until now, the bonding and characteristics of the interface between deposited nanoparticles and the substrate surface has not been known. It is investigated using X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy to characterize an electropolished NiTi stent surface coated by laser-generated Au and Ti nanoparticles. The deposition of elemental Au and Ti nanoparticles is observed on the total 3D surface. Ti-coated samples are composed of Ti oxide and Ti carbide because of nanoparticle fabrication and the coating process carried out in 2-propanol. The interface between nanoparticles and the electropolished surface consists of a smooth, monotone elemental depth profile. The interface depth is higher for the Ti nanoparticle coating than for the Au nanoparticle coating. This smooth depth gradient of Ti across the coating-substrate intersection and the thicker interface layer indicate the hard bonding of Ti-based nanoparticles on the surface. Accordingly, electron microscopy reveals nanoparticles adsorbed on the surface without any sorption-blocking intermediate layer. The physicomechanical stability of the bond may benefit from such smooth depth gradients and direct, ligand-free contact. This would potentially increase the coating stability during stent application.     

Microwave spectrum,structure and dipole moment of cyclopentadienylberyllium hydride

Microwave spectra of C₅ H₅ BeH, C₅ H₅ BeD, ¹³CC₄ H₅ BeH, and ¹³CC₄ H₅ BeD are reported. The molecule is a C_5v symmetrical top. The BeH bond length was found to be 1.32 Å with an error limit of 0.01 Å and the CC bond length was determined as 1.423 Å with one standard deviation of 0.001 Å. The distance from the beryllium atom to the centre of the cyclopentadienyl ring, h, and the CH bond length were assumed to be 1.49 Å and 1.09 Å, respectively. The dipole moment was determined through the Stark effect to be 2.08 D with one standard deviation of 0.01 D. Four different vibrationally excited normal modes were identified and their frequencies determined by relative intensity measurements.     

Evidence for an exotic S= -2, Q= -2 baryon resonance in proton-proton collisions at the CERN SPS

Results of resonance searches in the Xi(-)pi(-), Xi(-)pi(+), Xi;(+)pi(-), and Xi;(+)pi(+) invariant mass spectra in proton-proton collisions at sqrt[s]=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi(-)pi(-) baryon resonance with mass of 1.862+/-0.002 GeV/c(2) and width below the detector resolution of about 0.018 GeV/c(2). The significance is estimated to be above 4.2sigma. This state is a candidate for the hypothetical exotic Xi(--)(3/2) baryon with S=-2, I=3 / 2, and a quark content of (dsdsū). At the same mass, a peak is observed in the Xi(-)pi(+) spectrum which is a candidate for the Xi(0)(3/2) member of this isospin quartet with a quark content of (dsus[-]d). The corresponding antibaryon spectra also show enhancements at the same invariant mass.     

Inclusive production of protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum

New data on the production of protons, anti-protons and neutrons in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The charged baryons are identified by energy loss measurement in a large TPC tracking system. Neutrons are detected in a forward hadronic calorimeter. Inclusive invariant cross sections are obtained in intervals from 0 to 1.9 GeV/c (0 to 1.5 GeV/c) in transverse momentum and from ?0.05 to 0.95 (?0.05 to 0.4) in Feynman x for protons (anti-protons), respectively. p _T integrated neutron cross sections are given in the interval from 0.1 to 0.9 in Feynman x. The data are compared to a wide sample of existing results in the SPS and ISR energy ranges as well as to proton and neutron measurements from HERA and RHIC.