Elliptical flow -- a signature for early pressure in ultrarelativistic nucleus-nucleus collisions

Elliptical energy flow patterns in non-central Au(11.7AGeV) on Au reactions have been studied employing the RQMD model. The strength of these azimuthal asymmetries is calculated comparing the results in two different modes of RQMD (mean field and cascade). It is found that the elliptical flow which is readily observable with current experimental detectors may help to distinguish different reasonable expansion scenarios for baryon-dense matter. The final asymmetries are very sensitive to the pressure at maximum compression, because they involve a partial cancelation between early squeeze-out and subsequent flow in the reaction plane. This cancelation can be expected to occur in a broad energy region covered by the current heavy ion fixed-target programs at BNL and at CERN.Comment: 14 pages LaTeX including 3 postscript figure

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

Evidence of early multi-strange hadron freeze-out in high energy nuclear collisions

Recently reported transverse momentum distributions of strange hadrons produced in Pb(158AGeV) on Pb collisions and corresponding results from the relativistic quantum molecular dynamics (RQMD) approach are examined. We argue that the experimental observations favor a scenario in which multi-strange hadrons are formed and decouple from the system rather early at large energy densities (around 1 GeV/fm$^3$). The systematics of the strange and non-strange particle spectra indicate that the observed transverse flow develops mainly in the late hadronic stages of these reactions.Comment: 4 pages, 4 figure

Systematic Study of the Kaon to Pion Multiplicity Ratios in Heavy-Ion Collisions

We present a systematic study of the kaon to pion multiplicity ratios (K+/pi+ and K-/pi-) in heavy-ion collisions from AGS to RHIC energy using the Relativistic Quantum Molecular Dynamics (RQMD) model. The model satisfactorily describes the available experimental data on K+/pi+ and K-/pi-. Within the model, we find that the strong increase of the ratios with the number of participants is mainly due to hadronic rescattering of produced mesons with ingoing baryons and their resonances. The enhancement of K/pi in heavy-ion collisions with respect to elementary p+p interactions is larger at AGS energy than SPS energy, and decreases smoothly with bombarding energy. The total multiplicity ratios at RHIC energy are predicted by RQMD to be K+/pi+ = 0.19 and K-/pi- = 0.15.Comment: 10 pages, 8 figures, RevTeX style. A section is added to discuss effects of rope formatio

Thermal analysis of hadron multiplicities from relativistic quantum molecular dynamics

Some questions arising in the application of the thermal model to hadron production in heavy ion collisions are studied. We do so by applying the thermal model of hadron production to particle yields calculated by the microscopic transport model RQMD(v2.3). We study the bias of incomplete information about the final hadronic state on the extraction of thermal parameters.It is found that the subset of particles measured typically in the experiments looks more thermal than the complete set of stable particles. The hadrons which show the largest deviations from thermal behaviour in RQMD(v2.3) are the multistrange baryons and antibaryons. We also looked at the influence of rapidity cuts on the extraction of thermal parameters and found that they lead to different thermal parameters and larger disagreement between the RQMD yields and the thermal model.Comment: 12 pages, 2 figures, uses REVTEX, only misprint and stylistic corrections, to appear in Physical Review

A stopped Delta-Matter Source in Heavy Ion Collisions at 10 GeV/n

We predict the formation of highly dense baryon-rich resonance matter in Au+Au collisions at AGS energies. The final pion yields show observable signs for resonance matter. The Delta(1232) resonance is predicted to be the dominant source for pions of small transverse momenta. Rescattering effects -- consecutive excitation and deexcitation of Deltas -- lead to a long apparent lifetime (> 10 fm/c) and rather large volumina (several 100 fm^3) of the Delta-matter state. Heavier baryon resonances prove to be crucial for reaction dynamics and particle production at AGS.Comment: 17 pages, 5 postscript figures, uses psfig.sty and revtex.st

Analysis of hadron production in nucleus-nucleus interactions up to and out of kinematical limit of free NN-collisions in the frame of FRITIOF model

In the framework of the modified FRITIOF model, the inclusive spectra of the cumulative $\pi ^0$-, $\pi ^-$-mesons and protons produced in the nucleus-nucleus interactions at 4.5 GeV/c/nucleon and 4.2 GeV/c/nucleon are calculated. It is shown that the model reproduces qualitatively, and in some cases quantitatively the main experimental regularities of $\pi$-mesons production, and "soft" part of the proton spectra. According to the model the production of the cumulative particles is connected with the mechanism of the "soft" nucleon-nucleon interaction.Comment: 12 pages, 11 figure

Antibaryons in massive heavy ion reactions: Importance of potentials

In the framework of RQMD we investigate antiproton observables in massive heavy ion collisions at AGS energies and compare to preliminary results of the E878 collaboration. We focus here on the considerable influence of the *real* part of an antinucleon--nucleus optical potential on the antiproton momentum spectra

Dystonia: sparse synapses for D2 receptors in striatum of a DYT1 knock-out mouse model

Dystonia pathophysiology has been partly linked to downregulation and dysfunction of dopamine D2 receptors in striatum. We aimed to investigate the possible morpho-structural correlates of D2 receptor downregulation in the striatum of a DYT1 Tor1a mouse model. Adult control Tor1a+/+ and mutant Tor1a+/− mice were used. The brains were perfused and free-floating sections of basal ganglia were incubated with polyclonal anti-D2 antibody, followed by secondary immune-fluorescent antibody. Confocal microscopy was used to detect immune-fluorescent signals. The same primary antibody was used to evaluate D2 receptor expression by western blot. The D2 receptor immune-fluorescence appeared circumscribed in small disks (~0.3–0.5 μm diameter), likely representing D2 synapse aggregates, densely distributed in the striatum of Tor1a+/+ mice. In the Tor1a+/− mice the D2 aggregates were significantly smaller (μm2 2.4 ± SE 0.16, compared to μm2 6.73 ± SE 3.41 in Tor1a+/+) and sparse, with ~30% less number per microscopic field, value correspondent to the amount of reduced D2 expression in western blotting analysis. In DYT1 mutant mice the sparse and small D2 synapses in the striatum may be insufficient to “gate” the amount of presynaptic dopamine release diffusing in peri-synaptic space, and this consequently may result in a timing and spatially larger nonselective sphere of influence of dopamine action