Magnetic behavior in the incommensurate phase ∼LaCrS3:: effect of the partial substitution of Cr by Ti on the magnetic properties

Dilution of the magnetic interactions between Cr³⁺ ions by Ti³⁺ ions was observed in the CrS₂ layer of the misfit-layer compound ∼LaCrS₃. Pure ∼LaCrS₃ has complex magnetic properties which are reminiscent of spin glass behavior. This magnetic behavior comes from both the modulated character of the structure and the magnetic frustration of the planar-antiferromagnetic-triangular network of Cr³⁺ ions. Thus, there is a large hysteresis between the zero field cooled and the field cooled magnetic susceptibility curves below the transition temperature (≈75 K). Formation of a solid solution ∼LaCr_1−xTi_xS₃ by the addition of Ti³⁺ ions results in the decrease of transition temperature up to a doping level of x≈0.5, where the transition is no longer observed. The magnetic behavior of the phase with x≈0.5 is similar to that of several random exchange antiferromagnetic compounds.     

On the precision of calculations of initial state radiation in the LEP Z line-shape fits

Calculation of initial state radiation (ISR) in the fitting program MIZA and in the Standard Model program BHM is improved within the analysis of the Z line-shape measurements at LEP. The uncertainty on the determination of the Z line-shape parameters coming from the precision of ISR calculations is 2×10⁻⁴ on σ₀ and 0.1 MeV on m_Z and Γ_Z.     

Exotic quantum order in low-dimensional systems

Strongly correlated quantum systems in low dimensions often exhibit novel quantum ordering. This ordering is sometimes hidden and can be revealed only by examining new “dual” types of correlations. Such ordering leads to novel collection modes and fractional quantum numbers. Examples will be presented from quantum spin chains and the quantum Hall effect.     

Fragmentation cross sections of relativistic 208Pb projectiles

Production cross sections of more than 270 isotopes ranging from Z = 59 to Z = 82 were measured in the reaction ²⁰⁸Pb(1 GeV A)+Cu. The method of identifying the projectile fragments and evaluating the production cross sections is described. The experimental data are compared with a modern version of the abrasion-ablation model and with the empirical parameterization EPAX. Apart from deviations in the details they both show an overall good agreement. The cross sections of those fragments which are produced by the removal of protons only test the lower part of the excitation energy distribution. For the first time, the four-proton removal channel could be observed.     

Antikaon production in proton-nucleus reactions and the K− properties in nuclear matter

We calculate the momentum-dependent potentials for K⁺ and K⁻ mesons in a dispersion approach at nuclear density ϱ₀ using the information from the vacuum K⁺N and K⁻N scattering amplitudes, however, leaving out the resonance contributions for the in-medium analysis. Whereas the K⁺ potential is found to be repulsive (≈ + 25 MeV) and to show only a moderate momentum dependence, the K⁻ self-energy at normal nuclear matter density turns out to be ≈ − 140 ± 25 MeV at zero momentum roughly in line with K⁻ atomic data, however, decreases rapidly in magnitude for higher momenta. The antikaon production in p + A reactions is calculated within a coupled channel transport approach and compared to the data at KEK including different assumptions for the antikaon potentials. Furthermore, detailed predictions are made for p+¹²C and p+²⁰⁷Pb reactions at 2.5 GeV in order to determine the momentum-dependent antikaon potential experimentally.     

Inclusive one- and two-jet cross sections in γγ reactions at e+e− colliders

We have calculated inclusive one- and two jet production in photon-photon collisions superimposing direct, single-resolved and double-resolved cross sections for center of mass energies of the LEP1, LEP2 and NLC range. The direct and single-resolved cross sections are calculated up to next-to-leading order. The double-resolved two-jet cross section is calculated only in LO with a k factor estimated from the NLO one jet cross section. Various differential cross sections as functions of transverse momenta and rapidities of the jets are evaluated.     

Facile one-step sonochemical synthesis of ultrafine and stable fluorescent C-dots

This work describes a one-step synthesis of carbon dots (C-dots), which is carried out by sonication of polyethylene glycol (PEG-400) for 0.5–3 h. The effect of the various experimental parameters, such as sonication time, amplitude and temperature on the size and the fluorescence of the C-dots was studied. It was found that the average diameter of the C-dots is between 2 and 9 nm, depending on the preparation conditions. The highest quantum yield of emission was ∼16%. These high fluorescence properties of the C-dots could be used for bioimaging and for solar cell applications.     

Modification of algebraic multigrid for effective GPGPU-based solution of nonstationary hydrodynamics problems

We present modification of algebraic multigrid algorithm for effective GPGPU-based solution of nonstationary hydrodynamics problems. The modification is easy to implement and allows us to reduce number of times when the multigrid setup is performed, thus saving up to 50% of computation time with respect to unmodified algorithm.     

Kinetics of muon catalyzed fusion processes in solid H/D mixture

This paper presents the final results of an experimental study of the kinetics of the muon catalysed fusion (MCF) in solid hydrogen-deuterium mixtures (H/D) at a temperature of 3 K. The experiment E742 was carried out on a TRIUMF meson facility in Canada. Four exposures were performed at different deuterium concentrations in the H/D mixture: c_d = 0.0005, 0.02, 0.15 and 0.75. A simultaneous analysis of the measured time distributions of the 5.5 MeV γ-quanta and the 5.3 MeV conversion muons obtained from nuclear fusion in the pdμ molecule allowed to extract the values of MCF chain parameters in the H/D mixture: the fusion partial rates for different nuclear spin states of the pdμ molecule, and the pdμ molecule formation rate. The experimental data fitting procedure was conducted in two ways: using solely the analytical formulae describing the kinetics of the MCF processes in the H/D mixture, and the detailed Monte Carlo simulation of the entire experiment. The results obtained by these two methods are consistent with each other and confirm the existence of the Wolfenstein-Gerstein effect.