acta physica slovaca

Abstract: The problem of deconvolution is common to many branches of science, technology, medicine, etc. It always occurs when it is necessary to remove an instrumental distortion from a measured signal. The deconvolution belongs to the category of inverse problems which are often ill-posed, incorrect - the existence, unambiguity and stability of the solution are not a priori warranted. Connections among various deconvolution methods will be indicated, some practical recommendations will be given and examples from the deconvolution of X-ray diffraction profiles will be presented.

Abstract: This letter establishes a procedure which determines an algebra of exotic particles by using a non-commuting coordinates. These particles obey fractional statistics and live in two-dimensional space.

Abstract: The propagators relating to delta-potentials are exactly determined according to the method of path decomposition. The determination uses, after a suitable choice of decomposition surfaces, the images method and the spectral decomposition of the propagator at x=0.

Abstract: A computer experiment was suggested for testing of suitable methods for morphological analysis of nanocomposite films. A computer model was prepared to study three-dimensional (3D) structural properties on the basis of two-dimensional (2D) projections or sections. Some of the suitable methods are shown. A special attention is devoted to Wigner-Seitz cells and reconstruction of 3D spatial distribution.

Abstract: Using the Klauder-Perelomov coherent states of the pseudoharmonic oscillator Hamiltonian, corresponding diagonal P-representation for the density matrix of the gas of pseudoharmonic oscillators in thermal equilibrium is constructed. With a help of this new result, some corresponding characteristic thermal expectation values are obtained.

Abstract: We examine the double Higgs production process with the reaction e+e-  --> bbHH. We evaluate the total cross-section of bbHH and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. The numerical computation is done for the Higgs mass range 100--200 GeV and for the energy which is expected to be available at a possible Next Linear e+e- Collider with a center-of-mass energy 500, 1000 GeV  and luminosity 1000 fb^-1.

Abstract: The gluon distribution function exponent, lambda_g, is calculated by using  power law behavior of gluon distribution function at small x. Also, at low x, the derivative of structure function with respect to t and the gluon distribution function are determined. In the calculations, the leading order Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations are used. The calculated values are compared with other methods. The obtained results are very close to the calculated values by the leading order Gluck, Reya and Vogt and in agreement with experimental data.

Abstract: We study the possible production, at future e+e- colliders and at LHC, of a new vector resonance rho associated with new strong physics that could be responsible for electroweak symmetry breaking. For the effective description of the vector resonance we introduce a modified Breaking Electroweak Symmetry Strongly model. Since the new resonance exhibits enhanced couplings to the W and Z bosons as well as to the top quark we concentrate on the processes e+e-  -->  tt and e+e-  --> \nu_e \nu_e tt. At LHC we study the rho production in the process pp  -->  rho tt with rho decaying to a W+W- pair. We calculate the cross sections of these processes and of the relevant backgrounds.

Abstract: The production of saxion in e+e- collider and the saxion decay  into two photons were calculated in detail. Based on results it shows that the saxion is stable in our universe and can play the role of the late decaying particle (LDP) in a dark matter. At the low bound of the saxion mass it can be a new candidate for the cold dark matter (CDM).

Abstract: The absolute differential scattering cross sections have been measured from the (t, t) experiments on the 100Mo at Et = 12 MeV using a tandem accelerator and a multichannel magnetic spectrograph. Optical model parameters have been obtained from an analysis of the data with an optical-model search programme.

Abstract: The magnitudes of four independent complex amplitudes and two relative phases  are determined  in kaon photoproduction in three fixed incident photon energies. In order to reconstruct such amplitude determination in addition to differential cross section, we require six polarization parameters at different kaon scattering angles. Six available polarization parameters are used to calculate the complex amplitudes. This analysis indicates that the initial orientation of the spin polarization of the target nuclei is determinant for the probability of spin to flip after the interaction . A comparison between these results and the solution of the partial wave analysis has been presented.

Abstract: A hybrid model is put forward for describing relativistic heavy ion collisions. The early interaction stage responsible for entropy creation is calculated within the transport  Quark-Gluon String Model resulting in an initial state. The passage to subsequent isoentropic expansion proceeds with exact account for all conservation laws. Relativistic 3D hydrodynamics with the mixed phase equation of state is applied to this expansion stage. Essential differences in evolution of a fireball, described within this model and one for the Bjorken regime, are noted. The in-medium modified e+e- spectra are studied  and confronted with the recent CERES/NA45 data for 8% central Pb+Au collisions at the bombarding energy 158 AGeV.

Abstract: The melting properties of Au_N (N=12,13,14) clusters have been investigated by constant energy Molecular Dynamics and Monte Carlo simulations on the basis of Sutton Chen potential. The minimum energy geometries of Au_12 and Au_14 are interesting because they are not ico-based in contrast to the other metal clusters with the same size. The melting temperatures of the clusters are reported and compared with the values given in the literature. Considerable reduction in the melting temperatures of the clusters has been found. The premelting stage of Au_14 is observed.

Abstract: We report total electron scattering cross sections (TCS) for SF6, SF5 CF3, and CF3I, molecules of interest to the plasma industry over the energy range from threshold to 2000 eV. We also report the total scattering cross sections for e-formaldehyde for which there are currently no theoretical or experimental results reported. The ionization cross sections for these targets are also estimated using the Deustch and Maerk formalism and are compared with Binary Encounter Bethe (BEB) data of Kim.

Abstract: Model calculation of second order susceptibilities for F_A color centers in wide band gap materials is reported. The second order optical nonlinearity in KCl:Li crystals due to F_A color centers evaluated theoretically. The density matrix formalism is employed and the equation of motion is solved by second order perturbation to evaluate the nonlinear optical susceptibility for second harmonic generation as well as frequency mixing. It is found that the system shows large resonance-enhanced second order susceptibilities ~10^-16 mV^-1 for color center concentration of ~10^23 m^-3. A scheme of phase matching in terms of anomalous dispersion of the centers and coherent length are discussed.

Abstract: The common formalism for quantitative analysis in photoelectron spectroscopy and Auger electron spectroscopy is based on the strait-line approximation (SLA) model. Within the SLA, elastic scattering and inelastic surface losses of signal electrons are neglected and ideally flat sample surfaces are assumed. When analyzing real sample surfaces, these assumptions are not usually fulfilled. As a consequence, non-negligible systematic error is introduced into the quantitative results. Based on the present knowledge of electron transport at solid surfaces, influences of electron elastic scattering, electron surface excitation effects, and surface roughness on photoelectron peak areas are reviewed together with the presently developed correcting procedures easy to use in practical surface analysis.

Abstract: We describe the influence of pre-treatment procedures on the adhesion of diamond films to WC-Co substrates. Annealing of substrates at 600 C in vacuum and repeated etching in different reactive solutions (Al(OH)2-COOH diluted in acetic acid, Murakami and HCl:HNO3) were studied with respect to their effectiveness in suppressing C diffusion into Co on the WC-Co surface. Substrates were coated with polycrystalline diamond films by the dual plasma HF CVD method. Raman spectra confirmed the existence of the diamond phase on all samples. Film surface morphology varied with the pre-treatment method used. Adhesion strength was evaluated using the scratch test.