On the Equation of State of Nuclear Matter in 158A GeV Pb+Pb Collisions

Within a hydrodynamical approach we investigate the sensitivity of single inclusive momentum spectra of hadrons in 158A GeV Pb+Pb collisions to three different equations of state of nuclear matter. Two of the equations of state are based on lattice QCD results and include a phase transition to a quark-gluon plasma. The third equation of state has been extracted from the microscopic transport code RQMD under the assumption of complete local thermalization. All three equations of state provide reasonable fits to data taken by the NA44 and NA49 Collaborations. The initial conditions before the evolution of the fireballs and the space-time evolution pictures differ dramatically for the three equations of state when the same freeze-out temperature is used in all calculations. However, the softest of the equations of state results in transverse mass spectra that are too steep in the central rapidity region. We conclude that the transverse particle momenta are determined by the effective softness of the equation of state during the fireball expansion.Comment: 4 pages, including 4 figures and 2 tables. For a PostScript file of the manuscript, you can also goto http://t2.lanl.gov/schlei/eprint.htm

Thermal photons as a measure for the rapidity dependence of the temperature

The rapidity distribution of thermal photons produced in Pb+Pb collisions at CERN-SPS energies is calculated within scaling and three-fluid hydrodynamics. It is shown that these scenarios lead to very different rapidity spectra. A measurement of the rapidity dependence of photon radiation can give cleaner insight into the reaction dynamics than pion spectra, especially into the rapidity dependence of the temperature.Comment: 3 Figure

Microscopic study of freeze-out in relativistic heavy ion collisions at SPS energies

The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding systems of heavy nuclei at 160 AGeV/$c$ are analyzed within the microscopic Quark Gluon String Model (QGSM). We found that even for the most heavy systems particle emission takes place from the whole space-time domain available for the system evolution, but not from the thin ''freeze-out hypersurface", adopted in fluid dynamical models. Pions are continuously emitted from the whole volume of the reaction and reflect the main trends of the system evolution. Nucleons in Pb+Pb collisions initially come from the surface region. For both systems there is a separation of the elastic and inelastic freeze-out. The mesons with large transverse momenta, $p_t$, are predominantly produced at the early stages of the reaction. The low $p_t$-component is populated by mesons coming mainly from the decay of resonances. This explains naturally the decreasing source sizes with increasing $p_t$, observed in HBT interferometry. Comparison with S+S and Au+Au systems at 11.6 AGeV/$c$ is also presented.Comment: REVTEX, 26 pages incl. 9 figures and 2 tables, to be published in the Physical Review

Characterization of microbial communities of biofilters by phospholipid fatty acid analysis and rRNA targeted oligonucleotide probes

The microbial community of a biofilter for waste gas treatment of an animal rendering plant was characterized by the analyses of the phospholipid fatty acids (PLFAs) of the filter material. For these analyses five samples of one filter were taken in intervals between one and two months. The main components of the PLFA profiles were straight chain saturated, monounsaturated and cyclopropyl fatty acids. Terminally branched and 10-methyl branched fatty acids were present in minor amounts. The structure and succession of the microbial community was interpreted by the presence and quantitative changes of diagnostic fatty acids. The stability of diagnostic fatty acids in relation to varying incubation parameters was tested for a number of bacterial isolates from biofilters representing different phylogenetic branches. For two samples, the data from the PLFA-analyses were compared with data obtained by hybridization with fluorescently labeled, rRNA-targeted oligonucleotide probes specific for the alpha-, beta- and gamma-subclass of the Proteobacteria, the Actinobacteria (Firmicutes with high G+C content) and the Firmicutes with low G+C content. These data indicated a dominating number of Proteobacteria (54% and 35% of DAPI-stained cells), in which the gamma-Proteobacteria represented the main fraction. Actinobacteria were detected in minor amounts, the number of Firmicutes with low G+C content was near the detection limit of the method. About half of the cells detected with a probe specific fur Bacteria did not hybridize with the probes specific for the alpha-, beta- and gamma subclass of the Pruteobacteria and the two subgroups of the Firmicutes. The results of both methods, the fluorescence in situ hybridization (FISH) and the PLFA analyses corresponded well and were best suited to confirm and complement each other