343 research outputs found
Sudden freeze-out vs continuous emission: duality in hydro-kinetic approach to A+A collisions
The problem of spectra formation in hydrodynamic approach to A+A collisions
is discussed. It is analyzed in terms of the two different objects:
distribution and emission functions. We show that though the process of
particle liberation, described by the emission function, is, usually,
continuous in time, the observable spectra can be also expressed by means of
the Landau/Cooper-Frye prescription. We argue that such an approximate duality
results from some symmetry properties that systems in A+A collisions reach to
the end of hydrodynamic evolution and reduction of the collision rate at post
hydrodynamic stageComment: 6 pages, talk presented by S.V. Akkelin during the 3rd Budapest
Winter School on Heavy Ion Physics, Dec. 8-11, 2003, Budapest, Hungar
Tubular initial conditions and ridge formation
The 2D azimuth & rapidity structure of the two-particle correlations in
relativistic A+A collisions is altered significantly by the presence of sharp
inhomogeneities in superdense matter formed in such processes. The causality
constraints enforce one to associate the long-range longitudinal correlations
observed in a narrow angular interval, the so-called (soft) ridge, with
peculiarities of the initial conditions of collision process. This study's
objective is to analyze whether multiform initial tubular structures,
undergoing the subsequent hydrodynamic evolution and gradual decoupling, can
form the soft ridges. Motivated by the flux-tube scenarios, the initial energy
density distribution contains the different numbers of high density tube-like
boost-invariant inclusions that form a bumpy structure in the transverse plane.
The influence of various structures of such initial conditions in the most
central A+A events on the collective evolution of matter, resulting spectra,
angular particle correlations and v_n-coefficients is studied in the framework
of the HydroKinetic Model (HKM).Comment: 18 pages, 6 figures, the paper to be published in Advances of High
Energy Physics (2013, in press
Hydrokinetic predictions for femtoscopy scales in A+A collisions in the light of recent ALICE LHC results
A study of energy behavior of the pion spectra and interferometry scales is
carried out for the top SPS, RHIC and for LHC energies within the hydrokinetic
approach. The main mechanisms that lead to the paradoxical, at first sight,
dependence of the interferometry scales with an energy growth, in particular, a
decrease ratio, are exposed. The hydrokinetic predictions
for the HBT radii at LHC energies are compared with the recent results of the
ALICE experiment.Comment: Based on the talks given at the Sixth Workshop on Particle
Correlations and Femtoscopy, BITP, Kiev, September 14 - 18, 2010 and GSI/EMMI
Seminar, January 14, 201
Feeding of the elliptic flow by hard partons
We propose that in nuclear collisions at the LHC the elliptic flow may get a
contribution from leading hard and semihard partons which deposit energy and
momentum into the hydrodynamic bulk medium. The crucial effect is that these
partons induce wakes which interact and merge if they come together. The
contribution to the integrated elliptic flow is estimated with the help of a
toy model to about 25% of the observed value and shows strong event-by-event
fluctuations.Comment: 9 pages, 3 figure
Fast hadron freeze-out generator, part II: noncentral collisions
The fast Monte Carlo procedure of hadron generation developed in our previous
work is extended to describe noncentral collisions of nuclei. We consider
different possibilities to introduce appropriate asymmetry of the freeze-out
hyper-surface and flow velocity profile. For comparison with other models and
experimental data we demonstrate the results based on the standard
parametrizations of the hadron freeze-out hyper-surface and flow velocity
profile assuming either a common chemical and thermal freeze-out or the
chemically frozen evolution from chemical to thermal freeze-out. The C++
generator code is written under the ROOT framework and is available for public
use at http://uhkm.jinr.ru/Comment: 27 pages including 7 figures as EPS-files; prepared using LaTeX
package for publication in Physical Review
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