Understanding the rapidity dependence of the elliptic flow and the HBT radii at RHIC

The pseudo-rapidity dependence of the elliptic flow at various excitation energies measured by the PHOBOS Collaboration in Au+Au collisions at RHIC is one of the surprising results that has not been explained before in terms of hydrodynamical models. Here we show that these data are in agreement with theoretical predictions and satisfy the universal scaling relation predicted by the Buda-Lund hydrodynamical model, based on exact solutions of perfect fluid hydrodynamics. We also show a theoretical prediction on the rapidity and transverse momentum scaling of the HBT radii measured in heavy ion collisions, based on the Buda-Lund model.Comment: 6 pages, 2 figures, proceedings contribution for M. Csanad's talk at the Workshop on Particle Correlations and Femtoscopy 2005, Kromeri

An indication for deconfinement in Au+Au collisions at RHIC

We present simultaneous, quality fits to final BRAHMS, PHENIX, PHOBOS and STAR data on particle spectra and two-particle Bose-Einstein or HBT correlations as measured in Au+Au collisions at $\sqrt{s_{NN}} = 130$ GeV. Using the Buda-Lund hydro model, the best fit is achieved when the most central 1/8th of the particle emitting volume is superheated to $T > T_c =170$ MeV. In contrast, we find no indication for such a hot central region in a similar analysis of Pb+Pb data at CERN SPS.Comment: 6 pages, 2 figures, 1 table, presented by A. Ster at the XXXIIIth International Symposium on Multiparticle Dynamics, Cracow, Poland, Sept. 200

A hint at quark deconfinement in 200 GeV Au+Au data at RHIC

We give the emission function of the axially symmetric Buda-Lund hydro model and present its simultaneous, high quality fits to identified particle spectra, two-particle Bose-Einstein or HBT correlations and charged particle pseudorapidity distributions as measured by BRAHMS and PHENIX in 0-30 % central, \sqrt{s_{\NN}} = 200 GeV Au+Au collisions at RHIC. The best fit is achieved when the most central region of the particle emitting volume is superheated to $T_0 = 200 \pm 9$ MeV $\ge T_c =172 \pm 3$ MeV, a preliminary, 3 $\sigma$ effect.Comment: 10 pages, 3 figures, talk of A. Ster at the 2nd Warsaw Meeting on Correlations and Resonances in HIC, see http://hirg.if.pw.edu.pl/en/meeting/oct2003/talks/csorgo/Ster.pp

From Quark Gluon Plasma to a Perfect Fluid of Quarks and Beyond

With high energy heavy ion collisions one tries to create a new forms of matter that is similar to the one present at the birth of our Universe. Recent development on flow pattern, initial energy-density and freeze-out temperature shows that most likely this new form of matter is in a deconfined state, has colored degrees of freedom and is more fluid-like than gas-like. In present paper we calculate estimations on the physical properties of this new-old matter.Comment: 10 pages, 5 figures, to appear in the proceedings of the 44th International School of Subnuclear Physics, Erice, Sicily, 29 August - 7 September 200

HIV with contact-tracing: a case study in Approximate Bayesian Computation

Missing data is a recurrent issue in epidemiology where the infection process may be partially observed. Approximate Bayesian Computation, an alternative to data imputation methods such as Markov Chain Monte Carlo integration, is proposed for making inference in epidemiological models. It is a likelihood-free method that relies exclusively on numerical simulations. ABC consists in computing a distance between simulated and observed summary statistics and weighting the simulations according to this distance. We propose an original extension of ABC to path-valued summary statistics, corresponding to the cumulated number of detections as a function of time. For a standard compartmental model with Suceptible, Infectious and Recovered individuals (SIR), we show that the posterior distributions obtained with ABC and MCMC are similar. In a refined SIR model well-suited to the HIV contact-tracing data in Cuba, we perform a comparison between ABC with full and binned detection times. For the Cuban data, we evaluate the efficiency of the detection system and predict the evolution of the HIV-AIDS disease. In particular, the percentage of undetected infectious individuals is found to be of the order of 40%

Buda-Lund hydro model and the elliptic flow at RHIC

The ellipsoidally symmetric Buda-Lund hydrodynamic model describes naturally the transverse momentum and the pseudorapidity dependence of the elliptic flow in Au+Au collisions at roots(NN) = 130 and 200 GeV. The result confirms the indication of quark deconfinement in Au+Au collisions at RHIC, obtained from Buda-Lund hydro model fits to combined spectra and HBT radii of BRAHMS, PHOBOS, PHENIX and STAR

Oscillating HBT radii and the time evolution of the source-√s NN = 200 GeV Au + Au data analyzed with azimuthally sensitive Buda-Lund hydro model

Identified particle spectra of pions, kaons and (anti)protons, and elliptic flow and azimuthal dependence of Bose-Einstein or HBT correlations of identified pions in sNN = 200 GeV Au + Au collisions is analyzed simultaneously using an ellipsoidally symmetric generalization of the Buda-Lund hydrodynamical model. The transverse flow is found to be faster in the reaction plane than out of plane, which results in a reaction zone that gets slightly more elongated in-plane than out of plane. © 2011 Pleiades Publishing, Ltd