28 research outputs found
Production of Light Nuclei in Heavy Ion Collisions via Hagedorn Resonances
The physical processes behind the production of light nuclei in heavy ion
collisions are unclear. The nice theoretical description of experimental yields
by thermal models conflicts with the very small binding energies of the
observed states, being fragile in such a hot and dense environment. Other
available ideas are delayed production via coalescence, or a cooling of the
system after the chemical freeze-out according a Saha equation, or a `quench'
instead of a thermal freeze-out. A recently derived prescription of an
(interacting) Hagedorn gas is applied to consolidate the above pictures. The
tabulation of decay rates of Hagedorn states into light nuclei allows to
calculate yields usually unaccessable due to very poor Monte Carlo statistics.
Decay yields of stable hadrons and light nuclei are calculated. While the
scale-free decays of Hagedorn states alone are not compatible with the
experimental data, a thermalized hadron and Hagedorn state gas is able to
describe the experimental data. Applying a cooling of the system according a
Saha-equation with conservation of nucleons and anti-nucleons in number leads
to (nearly) temperature independent yields, thus a production of the light
nuclei at temperatures much lower than the chemical freeze-out temperature is
possible.Comment: 7 pages, 6 figure
Medium modification of pion production in low energy Au+Au collisions
There is a major mismatch between the charged pion yields in Au+Au collisions
at low energies calculated by various transport models and the experimental
measured values from the HADES collaboration. In this work, reasonable
improvements on the equation of state, in-medium modification of cross
sections, and the influence of the nuclear potential for Delta resonances will
be investigated in the framework of the GiBUU transport model. As a result, we
demonstrate that theoretical calculations can indeed describe the charged pion
yields measured by HADES for Au+Au collisions rather well, but that a mismatch
then remains between calculations and data for the yields of neutral pions
extracted from dileptons within the same experiment.Comment: 14 pages, 16 figure
QCD Matter Thermalization at RHIC and LHC
Employing the perturbative QCD inspired parton cascade, we investigate
kinetic and chemical equilibration of the partonic matter created in central
heavy ion collisions at RHIC and LHC energies. Two types of initial conditions
are chosen. One is generated by the model of wounded nucleons using the PYTHIA
event generator and Glauber geometry. Another is considered as a color glass
condensate. We show that kinetic equilibration is almost independent on the
chosen initial conditions, whereas there is a sensitive dependence for chemical
equilibration. The time scale of thermalization lies between 1 and 1.5 fm/c.
The final parton transverse energy obtained from BAMPS calculations is compared
with the RHIC data and is estimated for the LHC energy.Comment: 8 pages, 10 figures, plenary talk at International Conference on
Strangeness in Quark Matter 2008, Beijing, China, October 6-10, 200