Transverse hydrodynamics with sudden hadronization -- production of strangeness

We consider a physical scenario for ultra-relativistic heavy-ion collisions where, at the early stage, only transverse degrees of freedom of partons are thermalized, while the longitudinal motion is described by free streaming. When the energy density of the partonic system drops to a certain critical value, the partons hadronize and the newly formed hadronic system freezes out. This sudden change is described with the help of the Landau matching conditions followed by the simulations done with THERMINATOR. The proposed scenario reproduces well the transverse-momentum spectra, the elliptic flow coefficient v2, and the HBT radii of pions and kaons studied at RHIC (Au+Au collisions at the top beam energy). It also reproduces quite well the transverse-momentum spectra of hyperons.Comment: talk presented by WF at the Strangeness in Quark Matter Conference, Buzios, Brazil, Sept. 27 - oct. 2, 200

Resonance Production in RHIC Collisions

Results of resonance particle production measured at RHIC in $\sqrt{s_{\rm NN}} =$ 200 GeV Au+Au collisions are compared to measurements in p+p and d+Au collisions in order to verify the existence of an extended hardronically interacting medium. Yield and momentum distributions of resonances maybe modified during the fireball lifetime due to resonance decay and the subsequent rescattering of their decay daughters as well as the regeneration of resonances from their decay products. Modified momentum spectra in heavy ion collisions may change the nuclear modification factor R$_{\rm AA}$. The influence on the elliptic flow v$_{2}$ due to late regeneration of resonances is discussed.Comment: 6 pages, 6 figures, Proceedings of the 22st Winter Workshop on Nuclear Dynamics, San Diago, California, 12-18 March, 200

Calculation of Screening Masses in a Chiral Quark Model

We consider a simple model for the coordinate-space vacuum polarization function which is often parametrized in terms of a screening mass. We discuss the circumstances in which the standard result for the screening mass, $m_{sc}=\pi T$, is obtained. In the model considered here, that result is obtained when the momenta in the relevant vacuum polarization integral are small with respect to the first Matsubara frequency.Comment: 6 pages, 2 figure

Strong Color Field Baryonic Remnants in Nucleus-Nucleus Collisions at 200A GeV

The effects of strong color electric fields (SCF) on the baryon production at RHIC are studied in the framework of HIJING/B\=B (v2.0) model. The particle species dependence of nuclear modification factors (NMF) are analyzed for Au+Au collisions at 200A GeV. A doubling of the string tension leading to a modification of the strangeness suppression according to Schwinger mechanism is shown to provide an alternate explanation to coalescence models for the interpretation of the observed baryon and meson production at moderate $p_T$ and results in a predicted enhancement in the (multi)strange (anti)hyperon production.Comment: 6 pages, Latex(Revtex), 4 figures;Added new references, one figure, text slightly modified. final version accepted for publication in Pnys. Rev. C (october,05

Quark Potential in a Quark-Meson Plasma

We investigate quark potential by considering meson exchanges in the two flavor Nambu--Jona-Lasinio model at finite temperature and density. There are two kinds of oscillations in the chiral restoration phase, one is the Friedel oscillation due to the sharp quark Fermi surface at high density, and the other is the Yukawa oscillation driven by the complex meson poles at high temperature. The quark-meson plasma is strongly coupled in the temperature region $1\le T/T_c \lesssim 3$ with $T_c$ being the critical temperature of chiral phase transition. The maximum coupling in this region is located at the critical point.Comment: 8 pages and 8 figure

Comment on ``Relativistic kinetic equations for electromagnetic, scalar and pseudoscalar interactions''

It is found that the extra quantum constraints to the spinor components of the equal-time Wigner function given in a recent paper by Zhuang and Heinz should vanish identically. We point out here the origin of the error and give an interpretation of the result. However, the principal idea of obtaining a complete equal-time transport theory by energy averaging the covariant theory remains valid. The classical transport equation for the spin density is also found to be incorrect. We give here the correct form of that equation and discuss briefly its structure.Comment: 5 pages LaTe

Meson Correlation Function and Screening Mass in Thermal QCD

Analytical results for the spatial dependence of the correlation functions for all meson excitations in perturbative Quantum Chromodynamics, the lowest order, are calculated. The meson screening mass is obtained as a large distance limit of the correlation function. Our analysis leads to a better understanding of the excitations of Quark Gluon Plasma at sufficiently large temperatures and may be of relevance for future numerical calculations with fully interacting Quantum Chromodynamics.Comment: 11 page

Spatial and Temporal Hadron Correlators below and above the Chiral Phase Transition

Hadronic correlation functions at finite temperature in QCD, with four flavours of dynamical quarks, have been analyzed both above and below the chiral symmetry restoration temperature. We have used both point and extended sources for spatial as well as temporal correlators. The effect of periodic temporal boundary conditions for the valence quarks on the spatial meson correlators has also been investigated. All our results are consistent with the existence of individual quarks at high temperatures. A measurement of the residual interaction between the quarks is presented.Comment: 19 pages HLRZ 54/93, BI-TP 93/76, TIFR/TH/94-1

Chiral symmetry breaking in hot matter

This series of three lectures covers (a) a basic introduction to symmetry breaking in general and chiral symmetry breaking in QCD, (b) an overview of the present status of lattice data and the knowlegde that we have at finite temperature from chiral perturbation theory. (c) Results obtained from the Nambu--Jona-Lasinio model describing static mesonic properties are discussed as well as the bulk thermodynamic quantities. Divergences that are observed in the elastic quark-antiquark scattering cross-section, reminiscent of the phenomenon of critical opalescence in light scattering, is also discussed. (d) Finally, we deal with the realm of systems out of equilibrium, and examine the effects of a medium dependent condensate in a system of interacting quarks.Comment: 62 LaTex pages, incorporating 23 figures. Lectures given at the eleventh Chris-Engelbrecht Summer School in Theoretical Physics, 4-13 February, 1998, to be published by Springer Verla

Impact of Nucleon Mass Shift on the Freeze Out Process

The freeze out of a massive nucleon gas through a finite layer with time-like normal is studied. The impact of in-medium nucleon mass shift on the freeze out process is investigated. A considerable modification of the thermodynamical variables temperature, flow-velocity, energy density and particle density has been found. Due to the nucleon mass shift the freeze out particle distribution functions are changed noticeably in comparison with evaluations, which use vacuum nucleon mass.Comment: submitted to Physical Review