Elastic Pion Scattering on the Deuteron in a Multiple Scattering Model

Pion elastic scattering on deuterium is studied in the KMT multiple scattering approach developed in momentum space. Using a Paris wave function and the same methods and approximations as commonly used in pion scattering on heavier nuclei excellent agreement with differential cross section data is obtained for a wide range of pion energies. Only for $T_{\pi}>250$ MeV and very backward angles, discrepancies appear that are reminiscent of disagreements in pion scattering on $^3$He, $^3$H, and $^4$He. At low energies the second order corrections have been included. Polarization observables are studied in detail. While tensor analyzing powers are well reproduced, vector analyzing powers exhibit dramatic discrepancies.Comment: 25 pages LATEX and 9 postscript figures in a self-extracting uufile archiv

Pion interaction with the trinucleon up to the eta production threshold

Pion elastic, charge exchange scattering and induced eta production on the trinucleon systems are investigated in a coupled-channels approach in momentum space with Fadeev wave functions. The channel $\pi N \rightarrow \eta N$ is included using an isobar model with S-, P-, and D-wave resonances. While the coherent reactions like $^3$He($\pi,\pi)^3$He can be reasonably well reproduced up to $T_{\pi}$=500 MeV, large discrepancies appear for the incoherent processes, $^3$He($\pi^-,\pi^0)^3$H and $^3$He($\pi^-,\eta)^3$H at backward angles and energies above $\Delta$-resonance. In the forward direction the $(\pi,\eta)$ calculations underestimate the experimental measurements very close to threshold but agreement with the data improves with increasing pion energy. Predictions are made for the asymmetries of the various reactions on polarized $^3$He.Comment: 40 pages, 12 figures (available from the authors), Mainz preprint MKPH-T-92-1

Comprehensive Methodology for Investigation of Middle Fractions of Petroleum

A methodology has been developed for separation and identification of hydrocarbons of middle 250-350°C fractions of Taribani and Mirzaani petroleum (Georgia) in order to determine their individual hydrocarbon composition. The middle fractions of petroleum are difficult to study objects due to the huge variety of hydrocarbon isomers present in them.The methodology includes the following complex of physical and chemical methods for processing of petroleum: distillation, dearomatization by adsorption chromatography, thorough separation of isoalkanes from cycloalkanes using three stages thermal diffusion, processing of the obtained concentrates with thiocarbamide. To determine the individual composition of the fractions, instrumental methods of gasliquid chromatography analysis on capillary columns, MS and GC/MS were used. The developed methodology has been successfully applied to the separation of paraffinic, isoparaffinic and cycloparaffinic hydrocarbons and to determine molecular composition of the middle fractions. Separation of isomers from the concentrates obtained by way of thermal diffusion fractions of Taribani and Mirzaani petroleum was achieved and a number of isoprenoids of C11-C23 composition were identified, in thiocarbamide concentrates there were polycyclic alkanes of C11-C16 composition, and in filtrates - relict, polymethyl-substituted decalins of C14-C16 compositio