1,374 research outputs found
Remnants of Initial Anisotropic High Energy Density Domains in Nucleus-Nucleus Collisions
Anisotropic high energy density domains may be formed at early stages of
ultrarelativistic heavy ion collisions, e.g. due to phase transition dynamics
or non-equilibrium phenomena like (mini-)jets. Here we investigate hadronic
observables resulting from an initially created anisotropic high energy density
domain. Based on our studies using a transport model we find that the initial
anisotropies are reflected in the freeze-out multiplicity distribution of both
pions and kaons due to secondary hadronic rescattering. The anisotropy appears
to be stronger for particles at high transverse momenta. The overall kaon
multiplicity increases with large fluctuations of local energy densities, while
no change has been found in the pion multiplicity.Comment: Submitted to PR
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
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
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
Phasespace Correlations of Antideuterons in Heavy Ion Collisions
In the framework of the relativistic quantum molecular dynamics approach
({\small RQMD}) we investigate antideuteron () observables in
Au+Au collisions at 10.7~AGeV. The impact parameter dependence of the formation
ratios and is calculated. In central
collisions, the antideuteron formation ratio is predicted to be two orders of
magnitude lower than the deuteron formation ratio. The yield in
central Au+Au collisions is one order of magnitude lower than in Si+Al
collisions. In semicentral collisions different configuration space
distributions of 's and 's lead to a large
``squeeze--out'' effect for antideuterons, which is not predicted for the
's
Comparison of Experimental Data to the Relativistic Quantum Molecular Dynamics Model For Si+Au Collisions at 14.6 A GeV/c
Predictions from the RQMD model are systematically compared to recently
published charged hadron distributions of AGS Experiment 802 for central Si+Au
collisions at 14.6 GeV/, taking into account both the experimental
trigger condition and acceptance. The main features of the data, including
K production, can be understood quantitatively to better than 20\% within
the framework of the model, although several discrepancies are found, most
importantly for the proton spectra.Comment: 16 pages (TeX) plus 6 Postscript figures (tar-gz-compressed and
uuencoded
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+/â 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 (~0.3â0.5 ÎŒm diameter), likely representing D2 synapse aggregates, densely distributed in the striatum of Tor1a+/+ mice. In the Tor1a+/â mice the D2 aggregates were significantly smaller (ÎŒm2 2.4 ± SE 0.16, compared to ÎŒm2 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 âgateâ 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
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