Chemical and mechanical instabilities in high energy heavy-ion collisions

G Gervino ,Andrea Lavagno ,Daniele Pigato

doi:10.1088/1742-6596/626/1/012065

Abstract

We investigate the possible thermodynamic instability in a warm and dense nuclear medium where a phase transition from nucleonic matter to resonance-dominated Δ-matter can take place. Such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fluctuations on the isospin concentration) in asymmetric nuclear matter. Similarly to the liquid-gas phase transition, the nucleonic and the Δ-matter phase have a different isospin density in the mixed phase. In the liquid-gas phase transition, the process of producing a larger neutron excess in the gas phase is referred to as isospin fractionation. A similar effects can occur in the nucleon-Δ matter phase transition due essentially to a Δ− excess in the Δ-matter phase in asymmetric nuclear matter. In this context, we study the hadronic equation of state by means of an effective quantum relativistic mean field model with the inclusion of the full octet of baryons, the Δ-isobar degrees of freedom, and the lightest pseudoscalar and vector mesons. Finally, we will investigate the presence of thermodynamic instabilities in a hot and dense nuclear medium where phases with different values of antibaryon-baryon ratios and strangeness content may coexist. Such a physical regime could be in principle investigated in the future high-energy compressed nuclear matter experiments where will make it possible to create compressed baryonic matter with a high net baryon density.

Highlights

One of the very interesting aspects in nuclear astrophysics and in the heavy-ion collisions experiments is a detailed study of the thermodynamical properties of strongly interacting nuclear matter away from the nuclear ground state.The new accumulating data from x-ray satellites provide important information on the structure and formation of compact stellar objects
Concerning the structure, these data are at first sight difficult to interpret in a unique and selfconsistent theoretical scenario, since some of the observations indicate rather small radii and other observations indicate large values for the mass of the star
The information coming from experiments with heavy ions in intermediateand high-energy collisions is that the equation of state (EOS) depends on the energy beam and sensibly on the electric charge fraction Z/A of the colliding nuclei, especially at not too high temperature [1, 2, 3, 4]

Summary

Introduction

One of the very interesting aspects in nuclear astrophysics and in the heavy-ion collisions experiments is a detailed study of the thermodynamical properties of strongly interacting nuclear matter away from the nuclear ground state.The new accumulating data from x-ray satellites provide important information on the structure and formation of compact stellar objects. In this context we show that a hadron phase transition of the baryon-antibaryon plasma can take place in the physical region of finite net baryon density (ρ0 ≤ ρB < 2ρ0, where ρ0 is the nuclear saturation density) and temperature (T 120 ÷ 150 MeV).

Objectives

Results

Conclusion