9,047 research outputs found
A novel scenario for the production of antihyperons in relativistic heavy ion collisions
We elaborate on our recent suggestion on antihyperon production in
relativistic heavy ion collisions by means of multi-mesonic (fusion-type)
reactions. It will be shown that the (rare) antihyperons are driven towards
chemical equilibrium with pions, nucleons and kaons on a timescale of 1--3 fm/c
in a still moderately baryon-dense hadronic environment.Comment: 4 pages, 3 figures, Contr. to QM2001: 15th. International Conference
on Ultra-Relativistic Nucleus-Nucleus Collision
Importance of multi-mesonic fusion processes on (strange) antibaryon production
Sufficiently fast chemical equilibration of (strange) antibaryons in an
environment of nucleons, pions and kaons during the course of a relativistic
heavy ion collision can be understood by a `clustering' of mesons to build up
baryon-antibaryon pairs. This multi-mesonic (fusion-type) process has to exist
in medium due to the principle of detailed balance. Novel numerical
calculations for a dynamical setup are presented. They show that - at maximum
SPS energies - yields of each antihyperon specie are obtained which are
consistent with chemical saturated populations of T approximately 150-160 MeV,
in line with popular chemical freeze-out parameters extracted from thermal
model analyses.Comment: 14 pages, 8 figures; new version in standard reftex; version of
proceedings attached as postscript file; invited talk at CRIS2002, 4th
Catania Relativistic Ion Studies, Exotic Clustering, June 10-14, 200
Chemical Equilibration of Antihyperons
Rapid chemical equilibration of antihyperons by means of the interplay
between strong annihilation on baryons and the corresponding backreactions of
multi-mesonic (fusion-type) processes in the later, hadronic stage of an
ultrarelativistic heavy ion collision will be discussed. Explicit rate
calculations for a dynamical setup are presented. At maximum SPS energies
yields of each antihyperon specie are obtained which are consistent with
chemical saturated populations of MeV. The proposed
picture supports dynamically the popular chemical freeze-out parameters
extracted within thermal models.Comment: revised version for some typos and two references; 6 pages, 4
figures; contribution to the Int. Workshop XXX on Gross Properties of Nuclei
and Nuclear Excitations: Ultrarelativistic Heavy-Ion Collisions, Hirschegg,
Jan. 13 - 19, 200
Review of the "Bottom-Up" scenario
Thermalization of a longitudinally expanding color glass condensate with
Bjorken boost invariant geometry is investigated within parton cascade BAMPS.
Our main focus lies on the detailed comparison of thermalization, observed in
BAMPS with that suggested in the Bottom-Up scenario. We demonstrate that the
tremendous production of soft gluons via , which is shown in the
Bottom-Up picture as the dominant process during the early preequilibration,
will not occur in heavy ion collisions at RHIC and LHC energies, because the
back reaction hinders the absolute particle multiplication.
Moreover, contrary to the Bottom-Up scenario, soft and hard gluons thermalize
at the same time. The time scale of thermal equilibration in BAMPS calculations
is of order \as^{-2} (\ln \as)^{-2} Q_s^{-1}. After this time the gluon
system exhibits nearly hydrodynamic behavior. The shear viscosity to entropy
density ratio has a weak dependence on and lies close to the lower bound
of the AdS/CFT conjecture.Comment: Quark Matter 2008 Proceeding
Statistical description with anisotropic momentum distributions for hadron production in nucleus-nucleus collisions
The various experimental data at AGS, SPS and RHIC energies on hadron
particle yields for central heavy ion collisions are investigated by employing
a generalized statistical density operator, that allows for a well-defined
anisotropic local momentum distribution for each particle species, specified by
a common streaming velocity parameter. The individual particle ratios are
rather insensitive to a change in this new intensive parameter. This leads to
the conclusion that the reproduction of particle ratios by a statistical
treatment does not imply the existence of a fully isotropic local momentum
distribution at hadrochemical freeze-out, i.e. a state of almost complete
thermal equilibrium.Comment: 14 pages, revtex, 3 figures accepted version, to be published in
Journal of Physics
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