28 research outputs found
Ellipsoidal flows in relativistic hydrodynamics of finite systems
A new class of 3D anisotropic analytic solutions of relativistic
hydrodynamics with constant pressure is found. We analyse, in particular,
solutions corresponding to ellipsoidally symmetric expansion of finite systems
into vacuum. They can be utilized for relativistic description of the system
evolution in thermodynamic region near the softest point and at the final stage
of the hydrodynamic expansion in A+A collisions. The solutions can be used also
for testing of numerical hydrodynamic codes solving relativistic hydrodynamic
equations for anisotropic expansion of finite systemsComment: 7 pages, talk given at RHIC school 2004 (Budapest, december 2004
Correlation search for coherent pion emission in heavy ion collisions
The methods allowing to extract the coherent component of pion emission
conditioned by the formation of a quasi-classical pion source in heavy ion
collisions are suggested. They exploit a nontrivial modification of the quantum
statistical and final state interaction effects on the correlation functions of
like and unlike pions in the presence of the coherent radiation. The extraction
of the coherent pion spectrum from pi+pi-, pi+pi+ and pi-pi- correlation
functions and single--pion spectra is discussed in detail for large expanding
systems produced in ultra-relativistic heavy ion collisions.Comment: 21 pages, 3 eps figures, ReVTeX, corrected submission abstract.
Version published in PRC 65 (2002) 064904. Added is a detailed explanation of
the differences between pure coherent states and charge constrained coherent
states in the case of a simple example model. The expressions for
two-particle spectra taking into account both the final state interaction and
the coherent component of pion emission are derived in a more general and
transparent wa
Reconstruction of Hadronization Stage in Pb+Pb Collisions at 158A GeV/c
Recent data on hadron multiplicities in central Pb+Pb collisions at 158A
GeV/c at mid-rapidity are analyzed within the concept of chemical freeze-out. A
non-uniformity of the baryon chemical potential along the beam axis is taken
into account. An approximate analytical solution of the hydrodynamic equations
for a chemically frozen Boltzmann-like gas is found. The Cauchy conditions for
hydrodynamic evolution of the hadron resonance gas are fixed at the thermal
freeze-out hypersurface from analysis of one-particle momentum spectra and HBT
correlations. The proper time of chemical freeze-out and physical conditions at
the hadronization stage, such as energy density and averaged transverse
velocity, are found.Comment: 21 pages including 3 figures, RevTex, semi-relativistic solution of
hydrodynamics was used, submitted to Nucl. Phys.
Simple solutions of fireball hydrodynamics for self-similar elliptic flows
Simple, self-similar, elliptic solutions of non-relativistic fireball
hydrodynamics are presented, generalizing earlier results for spherically
symmetric fireballs with Hubble flows and homogeneous temperature profiles. The
transition from one dimensional to three dimensional expansions is investigated
in an efficient manner.Comment: 12 pages, 4 figures in 8 .eps files, references to recent data added,
accepted in Physics Letters
Interferometry search for new forms of matter in A+A collisions
A method allowing studies of the hadronic matter at the early evolution stage
in A+A collisions is developed. It is based on an interferometry analysis of
approximately conserved values such as the averaged phase-space density (APSD)
and the specific entropy of thermal pions. The plateau found in the APSD
behavior vs collision energy at SPS is associated, apparently, with the
deconfinement phase transition at low SPS energies; a saturation of this
quantity at the RHIC energies indicates the limiting Hagedorn temperature for
hadronic matter.Comment: 4 pages, 3 figures, contribution to the Quark Matter 2005
proceedings, minor change
Thermal phenomenology of hadrons from 200 AGeV S+S collisions
We develop a complete and consistent description for the hadron spectra from
heavy ion collisions in terms of a few collective variables, in particular
temperature, longitudinal and transverse flow. To achieve a meaningful
comparison with presently available data, we also include the resonance decays
into our picture. To disentangle the influences of transverse flow and
resonance decays in the -spectra, we analyse in detail the shape of the
-spectra.Comment: 31 pages, 13 figs in seperate uuencoded file, for LaTeX, epsf.sty and
dvips, TPR-93-16 and BNL-(no number yet
The freeze-out mechanism and phase-space density in ultrarelativistic heavy-ion collisions
We explore the consequences of a freeze-out criterion for heavy-ion
collisions, based on pion escape probabilities from the hot and dense but
rapidly expanding collision region. The influence of the expansion and the
scattering rate on the escape probability is studied. The temperature
dependence of this scattering rate favors a low freeze-out temperature of ~100
MeV. In general, our results support freeze-out along finite four-volumes
rather than sharp three-dimensional hypersurfaces, with high-pt particles
decoupling earlier from smaller volumes. We compare our approach to the
proposed universal freeze-out criteria using the pion phase-space density and
its mean free path.Comment: 8 pages, 2 figures, although conclusions are unchanged, the paper has
been re-written and the title has been changed for the sake of better
presentatio
On freeze-out problem in relativistic hydrodynamics
A finite unbound system which is equilibrium in one reference frame is in
general nonequilibrium in another frame. This is a consequence of the relative
character of the time synchronization in the relativistic physics. This puzzle
was a prime motivation of the Cooper--Frye approach to the freeze-out in
relativistic hydrodynamics. Solution of the puzzle reveals that the
Cooper--Frye recipe is far not a unique phenomenological method that meets
requirements of energy-momentum conservation. Alternative freeze-out recipes
are considered and discussed.Comment: 6 pages, 2 figures, references are corrected and updated, to be
published in the issue of Phys. Atom. Nucl. dedicated to S.T. Belyaev on the
occasion of his birthda
Two-particle BoseEinstein correlations in pp collisions at √s = 0.9 and 7 TeV measured with the ATLAS detector
The paper presents studies of Bose–Einstein Correlations (BEC) for pairs of like-sign charged particles measured in the kinematic range pT > 100 MeV and |η| <2.5 in proton–proton collisions at centre-of-mass energies of 0.9 and 7
TeV with the ATLAS detector at the CERN Large Hadron
Collider. The integrated luminosities are approximately 7
μb−1, 190 μb−1 and 12.4 nb-1 for 0.9 TeV,7 TeV minimum-bias and 7 TeV high-multiplicity data samples, respectively. The multiplicity dependence of the BEC parameters characterizing the correlation strength and the correlation source size are investigated for charged-particle multiplicities of up to 240. A saturation effect in the multiplicity dependence of the correlation source size parameter is observed using the high-multiplicity 7 TeV
data sample. The dependence of the BEC parameters on the average transverse momentum of the particle pair is also investigated
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On final conditions in high energy heavy ion Collisions
Motivated by the recent experimental observations, we discuss the freeze-out properties of the fireball created in central heavy ion collisions. We find that the freeze-out conditions, like temperature, velocity gradient near center of the fireball, are similar for different colliding systems and beam energies. This means that the transverse flow is stronger in the collisions of heavy nuclei than that of the light ones