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

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

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

Femtoscopic results in Au+Au and p+p from PHENIX at RHIC

Ultra-relativistic gold-gold and proton-proton collisions are investigated in the experiments of the Relativistic Heavy Ion Collider (RHIC). In the last several years large amount of results were revealed about the matter created in these collisions. The latest PHENIX results for femtoscopy and correlations are reviewed in this paper. Bose-Einstein correlations of charged kaons in 200 GeV Au+Au collisions and of charged pions in 200 GeV p+p collisions are shown. They are both compatible with previous measurements of charged pions in gold-gold collisions, with respect to transverse mass or number of participants scaling.Comment: Talk given at the VI Workshop on Particle Correlations and Femtoscopy, Kiev, September 14-18, 2010. 6 pages, 4 figures. This work was supported by the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi

Review of HBT or Bose-Einstein correlations in high energy heavy ion collisions

A brief review is given on the discovery and the first five decades of the Hanbury Brown - Twiss effect and its generalized applications in high energy nuclear and particle physics, that includes a meta-review. Interesting and inspiring new directions are also highlighted, including for example source imaging, lepton and photon interferometry, non-Gaussian shape analysis as well as many other new directions. Existing models are compared to two-particle correlation measurements and the so-called RHIC HBT puzzle is resolved. Evidence for a (directional) Hubble flow is presented and the conclusion is confirmed by a successful description of the pseudorapidity dependence of the elliptic flow as measured in Au+Au collisions by the PHOBOS Collaboration.Comment: 14 pages, 1 figure, 8 sub-figures, invited plenary talk at the ICPA-QGP 2005 conference in Kolkata, Indi

Testing the Resolving Power of 2-D K^+ K^+ Interferometry

Adopting a procedure previously proposed to quantitatively study two-dimensional pion interferometry, an equivalent 2-D chi^2 analysis was performed to test the resolving power of that method when applied to less favorable conditions, i.e., if no significant contribution from long lived resonances is expected, as in kaon interferometry. For that purpose, use is made of the preliminary E859 K^+ K^+ interferometry data from Si+Au collisions at 14.6 AGeV/c. As expected, less sensitivity is achieved in the present case, although it still is possible to distinguish two distinct decoupling geometries. The present analysis seems to favor scenarios with no resonance formation at the AGS energy range, if the preliminary K^+ K^+ data are confirmed. The possible compatibility of data with zero decoupling proper time interval, conjectured by the 3-D experimental analysis, is also investigated and is ruled out when considering more realistic dynamical models with expanding sources. These results, however, clearly evidence the important influence of the time emission interval on the source effective transverse dimensions. Furthermore, they strongly emphasize that the static Gaussian parameterization, commonly used to fit data, cannot be trusted under more realistic conditions, leading to distorted or even wrong interpretation of the source parameters!Comment: 11 pages, RevTeX, 4 Postscript figures include

Initial temperature and EoS of quark matter from direct photons

The time evolution of the quark gluon plasma created in gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) can be described by hydrodynamical models. Distribution of hadrons reflects the freeze-out state of the matter. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon spectra. Distributions of low energy photons was published in 2010 by PHENIX. In this paper we analyze a 3+1 dimensional solution of relativistic hydrodynamics and calculate momentum distribution of direct photons. Using earlier fits of this model to hadronic spectra, we compare photon calculations to measurements and find that the initial temperature of the center of the fireball is at least 519+-12 MeV, while for the equation of state we get c_s= 0.36+-0.02.Comment: Talk at the VI Workshop on Particle Correlations and Femtoscopy, Kiev, September 14-18, 2010. 6 pages, 1 figure. This work was supported by the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi

On Sums of Overlapping Products of Independent Bernoulli Random Variables

We find the exact distribution of an arbitrary remainder of an infinite sum of overlapping products of a sequence of independent Bernoulli random variables.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41634/1/11253_2004_Article_340347.pd