994 research outputs found
The Quark-Gluon Plasma in Equilibrium
Our current knowledge of the quark-gluon plasma in thermodynamical
equilibrium is reviewed. The phase diagram of strongly interacting matter is
discussed, with emphasis on the quark-hadron phase transition and the
color-superconducting phases of quark matter. Lattice QCD results on the order
of the phase transition, the thermodynamical functions, the heavy quark free
energy, mesonic spectral functions, and recent results for nonzero quark
chemical potential are presented. Analytic attempts to compute the
thermodynamical properties of strongly interacting matter, such as perturbation
theory, quasiparticle models, ``hard-thermal-loop''(HTL)-resummed perturbation
theory, the Polyakov-loop model, as well as linear sigma models are discussed.
Finally, color-superconducting quark matter is considered in the limit of weak
coupling. The gap equation and the excitation spectrum are derived. The
solution of the gap equation, gap parameters in various color-superconducting
phases, and critical temperatures for the transition to normal-conducting quark
matter are presented. A summary of gluon and photon properties in color
superconductors is given.Comment: 89 pages, 26 figures, review for Prog. Part. Nucl. Phys, minor
revisions to text, correction of typos, refs. adde
Remarks on the extraction of freeze-out parameters
I review the extraction of kinetic and chemical freeze-out parameters from
experimental data, with particular emphasis on the underlying assumptions and
the validity of the conclusions.Comment: 11 pages, 1 figure, proceedings of 'Quark Matter 2001', revised
version, refs. adde
Calculation of the expansion rate of the three-volume measure in high-energy heavy-ion collisions
In ultrarelativistic heavy-ion collisions the local three-volume measure is
expanding in the longitudinal and transverse directions. This is similar to the
Hubble-expansion of the universe, except that the former is not locally
isotropic. As an example the expansion rate is calculated assuming that the
energy-momentum tensor in the central region is that of an ideal fluid,
undergoing Bjorken flow in longitudinal direction, and with initial conditions
as expected for BNL-RHIC energy. While the longitudinal expansion of
three-volume is independent of the energy density of the fluid, in case of 3+1
dimensional expansion the form of the hydrodynamical solution (rarefaction wave
or deflagration shock) affects the three-volume expansion rate on the
hadronization hypersurface. As a consequence the average expansion rate on that
surface depends on the transverse size of the system. This may reflect in an
impact-parameter dependence of the formation probability of light nuclei and of
the freeze-out temperature of the strong interactions in the system.Comment: 10 Pages REVTEX, 4 Figures; Title slightly modified, 2 new figure
Relativistic Hydrodynamics for Heavy--Ion Collisions -- II. Compression of Nuclear Matter and the Phase Transition to the Quark--Gluon Plasma
We investigate the compression of nuclear matter in relativistic
hydrodynamics. Nuclear matter is described by a --type model for
the hadron matter phase and by the MIT bag model for the quark--gluon plasma,
with a first order phase transition between both phases. In the presence of
phase transitions, hydrodynamical solutions change qualitatively, for instance,
one-dimensional stationary compression is no longer accomplished by a single
shock but via a sequence of shock and compressional simple waves. We construct
the analytical solution to the ``slab-on-slab'' collision problem over a range
of incident velocities. The performance of numerical algorithms to solve
relativistic hydrodynamics is then investigated for this particular test case.
Consequences for the early compressional stage in heavy--ion collisions are
pointed out.Comment: 22 pages, 12 uuencoded figure
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