72 research outputs found
Transverse-Mass Effective Temperature in Heavy-Ion Collisions from AGS to SPS
Transverse-mass spectra in Au+Au and Pb+Pb collisions in incident energy
range from 2A to 160A GeV are analyzed within the model of 3-fluid dynamics. It
is shown that dynamical description of freeze-out, accepted in this model,
naturally explains the incident energy behavior of inverse-slope parameters of
these spectra observed in experiment. Simultaneous reproduction of the
inverse-slopes of all considered particles (protons, pions and kaons) suggests
that these particles belong to the same hydrodynamic flow at the instant of
their freeze-out.Comment: 4 pages, 3 figure
Relativistic Heavy-Ion Collisions within 3-Fluid Hydrodynamics: Hadronic Scenario
A 3-fluid hydrodynamic model for simulating relativistic heavy-ion collisions
is introduced. Alongside with two baryon-rich fluids, the new model considers
time-delayed evolution of a third, baryon-free (i.e. with zero net baryonic
charge) fluid of newly produced particles. Its evolution is delayed due to a
formation time, during which the baryon-free fluid neither thermalizes nor
interacts with the baryon-rich fluids. After the formation it starts to
interact with the baryon-rich fluids and quickly gets thermalized. Within this
model with pure hadronic equation of state, a systematic analysis of various
observables at incident energies between few and about 160A GeV has been done
as well as comparison with results of transport models. We have succeeded to
reasonably reproduce a great body of experimental data in the incident energy
range of E_{lab} = (1-160)A GeV. The list includes proton and pion rapidity
distributions, proton transverse-mass spectra, rapidity distributions of Lambda
and antiLambda hyperons, elliptic flow of protons and pions (with the exception
of proton v2 at 40A GeV), multiplicities of pions, positive kaons, phi-mesons,
hyperons and antihyperons, including multi-strange particles. This agreement is
achieved on the expense of substantial enhancement of the interflow friction as
compared to that estimated proceeding from hadronic free cross sections.
However, we have also found out certain problems. The calculated yield of K^-
is approximately by a factor of 1.5 higher than that in the experiment. We have
also failed to describe directed transverse flow of protons and pion at E_{lab}
> 40A GeV. This failure apparently indicates that the used EoS is too hard and
thereby leaves room for a phase transition.Comment: 30 pages, 20 figures, 2 tables. Version accepted for publication in
Phys. Rev.
Transverse-Mass Spectra in Heavy-Ion Collisions at energies E_{lab} = 2--160 GeV/nucleon
Transverse-mass spectra of protons, pions and kaons produced in collisions of
heavy nuclei are analyzed within the model of 3-fluid dynamics. It was
demonstrated that this model consistently reproduces these spectra in wide
ranges of incident energies E_{lab}, from 4A GeV to 160A GeV, rapidity bins and
centralities of the collisions. In particular, the model describes the
"step-like" dependence of kaon inverse slopes on the incident energy. The key
point of this explanation is interplay of hydrodynamic expansion of the system
with its dynamical freeze-out.Comment: 13 pages, 16 figures, summary is extended, version accepted by Phys.
Rev.
Representative elementary volume via averaged scalar Minkowski functionals
Representative Elementary Volume (REV) at which the material properties do
not vary with change in volume is an important quantity for making measurements
or simulations which represent the whole. We discuss the geometrical method to
evaluation of REV based on the quantities coming in the Steiner formula from
convex geometry. For bodies in the three-space this formula gives us four
scalar functionals known as scalar Minkowski functionals. We demonstrate on
certain samples that the values of such averaged functionals almost stabilize
for cells for which the length of edges are greater than certain threshold
value R. Therefore, from this point of view, it is reasonable to consider cubes
of volume R^3 as representative elementary volumes.Comment: 7 page
(3+1)-Dimensional Hydrodynamic Expansion with a Critical Point from Realistic Initial Conditions
We investigate a (3+1)-dimensional hydrodynamic expansion of the hot and
dense system created in head-on collisions of Pb+Pb/Au+Au at beam energies from
GeV. An equation of state that incorporates a critical end point (CEP)
in line with the lattice data is used. The necessary initial conditions for the
hydrodynamic evolution are taken from a microscopic transport approach (UrQMD).
We compare the properties of the initial state and the full hydrodynamical
calculation with an isentropic expansion employing an initial state from a
simple overlap model. We find that the specific entropy () from both
initial conditions is very similar and only depends on the underlying equation
of state. Using the chiral (hadronic) equation of state we investigate the
expansion paths for both initial conditions. Defining a critical area around
the critical point, we show at what beam energies one can expect to have a
sizable fraction of the system close to the critical point. Finally, we
emphasise the importance of the equation of state of strongly interacting
matter, in the (experimental) search for the CEP.Comment: 8 pages, 8 figure
Visualization of mechanical stress of near-surface layer by analyze of MFM images of planar permalloy microparticles formed on surface
The work was support by RFBR 17-08-00915
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