467 research outputs found
Non-boost-invariant motion of dissipative and highly anisotropic fluid
The recently formulated framework of anisotropic and dissipative
hydrodynamics (ADHYDRO) is used to describe non-boost-invariant motion of the
fluid created at the early stages of heavy-ion collisions. Very strong initial
asymmetries of pressure are reduced by the entropy production processes. By the
appropriate choice of the form of the entropy source we can reproduce realistic
scenarios for the isotropization expected in heavy-ion collisions. Our previous
results are generalized by including the realistic equation of state as the
limit of the isotropization processes.Comment: Version accepted for publication in Journal of Physics G: Nuclear and
Particle Physic
Locally anisotropic momentum distributions of hadrons at freeze-out in relativistic heavy-ion collisions
A spheroidal anisotropic local momentum distribution is implemented in the
statistical model of hadron production. We show that this form leads to exactly
the same ratios of hadronic abundances as the equilibrium distributions, if the
temperature is identified with a characteristic transverse-momentum scale.
Moreover, to a very good approximation the transverse-momentum spectra of
hadrons are the same for isotropic and anisotropic systems, provided the size
of the system at freeze-out is appropriately adjusted. We further show that
this invariance may be used to improve the agreement between the model and
experimental HBT results.Comment: 7 pages, 4 figure
Early anisotropic hydrodynamics and the RHIC early-thermalization and HBT puzzles
We address the problem if the early thermalization and HBT puzzles in
relativistic heavy-ion collisions may be solved by the assumption that the
early dynamics of the produced matter is locally anisotropic. The hybrid model
describing the purely transverse hydrodynamic evolution followed by the
perfect-fluid hydrodynamic stage is constructed. The transition from the
transverse to perfect-fluid hydrodynamics is described by the Landau matching
conditions applied at a fixed proper time. The global fit to the RHIC data
reproduces the soft hadronic observables (the pion, kaon, and the proton
spectra, the pion and kaon elliptic flow, and the pion HBT radii) with the
accuracy of about 20%. These results indicate that the assumption of the very
fast thermalization may be relaxed. In addition, the presented model suggests
that a large part of the inconsistencies between the theoretical and
experimental HBT results may be removed.Comment: replaced with the version published in Phys.Rev.C 8
Transverse hydrodynamics with sudden hadronization -- production of strangeness
We consider a physical scenario for ultra-relativistic heavy-ion collisions
where, at the early stage, only transverse degrees of freedom of partons are
thermalized, while the longitudinal motion is described by free streaming. When
the energy density of the partonic system drops to a certain critical value,
the partons hadronize and the newly formed hadronic system freezes out. This
sudden change is described with the help of the Landau matching conditions
followed by the simulations done with THERMINATOR. The proposed scenario
reproduces well the transverse-momentum spectra, the elliptic flow coefficient
v2, and the HBT radii of pions and kaons studied at RHIC (Au+Au collisions at
the top beam energy). It also reproduces quite well the transverse-momentum
spectra of hyperons.Comment: talk presented by WF at the Strangeness in Quark Matter Conference,
Buzios, Brazil, Sept. 27 - oct. 2, 200
Early dynamics of transversally thermalized matter
We argue that the idea that the parton system created in relativistic
heavy-ion collisions is formed in a state with transverse momenta close to
thermodynamic equilibrium and its subsequent dynamics at early times is
dominated by pure transverse hydrodynamics of the perfect fluid is compatible
with the data collected at RHIC. This scenario of early parton dynamics may
help to solve the problem of early equilibration.Comment: 4 pages, 2 figures, Talk given by M. Chojnacki at Quark Matter 2008,
Jaipur, Indi
Single-freeze-out model for ultra relativistic heavy-ion collisions at TeV and the LHC proton puzzle
The single-freeze-out model with parametrized hypersurface and flow geometry
is employed to analyze the transverse-momentum spectra of hadrons produced in
the Pb+Pb collisions at the collision energy of { TeV}
at the CERN Large Hadron Collider (LHC). With the notable exception for protons
and antiprotons, we find a very good agreement between the model results and
the data for the measured hadron species. The additional analysis of the HBT
radii of pions helps us to select, from several different types of freeze-out
studied in this work, the most realistic form of the freeze-out hypersurface.
We find that discrepancy ratio between the model and experiment for the
proton/antiproton spectra depends on , dropping from 2 in the soft region
to 1 around GeV.Comment: 9 pages, 10 figure
- …