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 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

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

Bose-Einstein correlations: a study of an invariance group

A group of transformations changing the phases of the single particle density matrix, but leaving unchanged the predictions for identical particles concerning the momentum distributions, momentum correlations etc., is identified. Its implications for the determinations of the interaction region from studies of Bose-Einstein correlations are discussed.Comment: 15 pages LateX + one figure ep

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

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

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

Emission times and opacities from interferometry in non-central Relativistic Nuclear Collisions

The nuclear overlap zone in non-central relativistic heavy ion collisions is azimuthally very asymmetric. By varying the angle between the axes of deformation and the transverse direction of the pair momenta, the transverse HBT radii oscillate in a characteristic way. It is shown that these oscillations allow determination of source sizes, deformations as well as the opacity and duration of emission of the source created in any non-central high energy nuclear collisions. The behavior of the physical quantities with centrality of the collisions is discussed --- in particular changes caused by a possible phase transition to a quark-gluon plasma.Comment: Revised version, to appear in Phys. Rev. Letter