104 research outputs found
On the formation of Hubble flow in Little Bangs
A dynamical appearance of scaling solutions in the relativistic hydrodynamics
applied to describe ultra-relativistic heavy-ion collisions is studied. We
consider the boost-invariant cylindrically symmetric systems and the effects of
the phase transition are taken into account by using a temperature dependent
sound velocity inferred from the lattice simulations of QCD. We find that the
transverse flow acquires the scaling form r/t within the short evolution times,
10 - 15 fm, only if the initial transverse flow originating from the
pre-equilibrium collective behavior is present at the initial stage of the
hydrodynamic evolution. The amount of such pre-equilibrium flow is correlated
with the initial pressure gradient; larger gradients require smaller initial
flow. The results of the numerical calculations support the phenomenological
parameterizations used in the Blast-Wave, Buda-Lund, and Cracow models of the
freeze-out process.Comment: 11 page
On the determinations of the size and shape of the interaction region from Bose-Einstein correlations
Determinations of the size and shape of the interaction region from
k-particle (k=1,2,...) momentum distributions of identical particles are
analyzed. The full group of transformations changing the single particle
density matrix without affecting any of the measurable momentum distributions
is identified. The corresponding uncertainties in the inferred parameters of
the interaction region are discussed.Comment: 13 pages Late
A method of eta' decay product selection to study partial chiral symmetry restoration
In case of chiral U_A(1) symmetry restoration the mass of the eta' boson (the
ninth, would-be Goldstone boson) is decreased, thus its production cross
section is heavily enhanced. The eta' decays (through one of its decay
channels) into five pions. These pions will not be correlated in terms of
Bose-Einsten correlations, thus the production enhancement changes the strength
of two-pion correlation functions at low momentum. Preliminary results strongly
support the mass decrease of the eta' boson. In this paper we propose a method
to select pions coming from eta' decays. We investigate the efficiency of the
proposed kinematical cut in several collision systems and energies with several
simulators. We prove that our method can be used in all investigeted collision
systems.Comment: Talk at the VI Workshop on Particle Correlations and Femtoscopy,
Kiev, September 14-18, 2010. 6 pages, 3 figures. This work was supported by
the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi
A Bose-Einstein Model of Particle Multiplicity Distributions
A model of particle production is developed based on a parallel with a theory
of Bose-Einstein condensation and similarities with other critical phenomena
such as critical opalescence. The role of a power law critical exponent tau and
Levy index alpha are studied. Various features of this model are developed and
compared with other commonly used models of particle production which are shown
to differ by having different values for tau, alpha. While void scaling is a
feature of this model, hierarchical structure is not a general property of it.
The value of the exponent tau=2 is a transition point associated with void and
hierarchical scaling features. An exponent gamma is introduced to describe
enhanced fluctuations near a critical point. Experimentally determined
properties of the void scaling function can be used to determine tau.Comment: Accepted for publication in Nucl. Phys.
Quantum-Statistical Correlations and Single Particle Distributions for Slowly Expanding Systems with Temperature Profile
Competition among particle evaporation, temperature gradient and flow is
investigated in a phenomenological manner, based on a simultaneous analysis of
quantum statistical correlations and momentum distributions for a
non-relativistic, spherically symmetric, three-dimensionally expanding, finite
source. The parameters of the model emission function are constrained by fits
to neutron and proton momentum distributions and correlation functions in
intermediate energy heavy-ion collisions. The temperature gradient is related
to the momentum dependence of the radius parameters of the two-particle
correlation function, as well as to the momentum-dependent temperature
parameter of the single particle spectrum, while a long duration of particle
evaporation is found to be responsible for the low relative momentum behavior
of the two-particle correlations.Comment: 20 pages + 5 ps figures, ReVTeX, uses psfig.sty, the description is
extended to include final state interactions, phenomenological evaporation
and to fit intermediate energy heavy ion proton and neutron spectrum and
correlation dat
Parametrization of Bose-Einstein correlations and reconstruction of the source function in hadronic Z-boson decays using the L3 detector
Bose-Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Levy stable distribution in conjunction with a hadronization model having highly correlated configuration and momentum space, the tau-model. Using these results, the source function is reconstructed
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