L. P. Csernai

Fluid dynamics and quark gluon string model: What we can expect for Au + Au collisions at 11.6-A/GeV/c

Abstract Central Au + Au collisions at 11.6 AGeV c are examined within the Quark Gluon String Model (QGSM) and one-Fluid Dynamical Model (FDM). QGSM is used to study baryon stopping and production of Δ — matter. FDM allows to extract measurable signatures of the transition of hadronic matter to Quark Gluon Plasma (QGP).

Initial state of ultrarelativistic heavy ion collisions

A model for energy, pressure, and flow velocity distributions at the beginning of ultrarelativistic heavy ion collisions is presented, which can be used as an initial condition for hydrodynamic calculations. Our model takes into account baryon recoil for both target and projectile, arising from the acceleration of partons in an effective field F mn produced in the collision. The typical field strength ~string tension! for RHIC energies is about 5‐12 GeV/fm, which allows us to talk about ‘‘string ropes.’’ The results show that a quark-gluon plasma forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. Such initial conditions may lead to the

Freeze-out in hydrodynamical models in relativistic heavy ion collisions

Freeze-out of particles across 3-dimensional space-time hypersurface with space-like normal is discussed in a simple kinetic model. The final momentum distribution of emitted particles shows a non-exponential transverse momentum spectrum, which is in quantitative agreement with recently measured SPS pion and

Neutron stars, hybrid stars and the equation of state

h^-

Large pt enhancement from freeze out

spectra.

Collectivity, energy density and baryon density in Pb on Pb collisions

Abstract Gross properties of hybrid stars consisting of a core of strange matter surrounded by ordinary neutron matter are investigated. We discuss star models based on phenomenological equations of state from nuclear reactions including a phase transition between the hadronic phase and the quark-gluon plasma. For certain parameters, such equations of state support the existence of hybrid stars. The identification of such objects could provide detailed information on the properties of strange quark matter.

Pion distributions from the fluid dynamical model of ultra-relativistic heavy ion collisions

Abstract Freeze out of particles across three dimensional space-time hypersurface is discussed in a simple kinetic model. The final momentum distribution of qemitted particles, for freeze out surfaces with space-like normal, shows a non-exponential transverse momentum spectrum. The slope parameter of the p t distribution increases with increasing p t , in agreement with recently measured SPS pion and h − spectra.

φ meson production at RHIC

Abstract Predictions of string and hydrodynamical models for 160 A GeV Pb on Pb reactions are discussed. Results of the quark-gluon string model suggest that complete stopping of nuclear matter is plausible at these energies. The results for baryon and energy densities in the two models are similar. These results support the continued application of the one-fluid dynamic model, particularly for later stages of the collisions.

Comparative analysis of strangeness production at AGS-BNL energies and SPS energies

Abstract Ultra-relativistic heavy ion reactions are described by a three dimensional, relativistic, perfect, one-fluid model. Numerical solutions are calculated for heavy ion reactions up to 60 GeV per nucleon. Observables are evaluated for emitted pions by adding the random thermal motion to the collective flow.

Pion distributions from the fluid dynamical model of ultra - relativistic heavy ion collisions

Abstract The production of φ mesons in Au+Au collisions at RHIC and their propagation in a hot and dense nuclear medium is studied within the microscopic quark-gluon string model. The inverse slope parameter of the transverse mass distribution agrees well with that extracted from the STAR data, while the absolute yield of φ is underestimated by a factor 2. It appears that the fusion of strings alone cannot increase the φ yield either. Less than 30% of detectable φs experience elastic scattering, this rate is insufficient for the full thermalization of φ. The directed flow of φ at ∣y∣≤ 2 demonstrates strong antiflow behavior, whereas its elliptic flow rises up to about 3.5% in the same rapidity interval. As a function of transverse momentum its rises linearly with increasing p t , in agreement with the STAR data, and saturates at p t > 2 GeV/c.