Phase-Space Coalescence for heavy and light quarks at RHIC

We review the application and successes of a phase-space coalescence plus fragmentation model that has been applied for hadronization at RHIC. The physical concept is discussed together with the practical implementation. The robustness of main predictions is reviewed together with several open issues like relevance of three dimensional calculation, finite width of the wave functions, effects of quark masses, energy-entropy conservation, space-momentum correlation. Eventually the relevance of coalescence also for the study of the microscopic interaction of heavy quarks is highlighted.Comment: Talk given at the Zimanyi 75 Memorial Workshop on "Hadronic and Quark Matter", Budapest, July 2-4, 2007. To appear in The European Physical Journal (Special Topics

Elliptic Flow and Shear Viscosity within a Transport Approach from RHIC to LHC Energy

We have investigated the build up of anisotropic flows within a parton cascade approach at fixed shear viscosity to entropy density \eta/s to study the generation of collective flows in ultra-relativistic heavy ion collisions. We present a study of the impact of a temperature dependent \eta/s(T) on the generation of the elliptic flow at both RHIC and LHC. Finally we show that the transport approach, thanks to its wide validity range, is able to describe naturally the rise - fall and saturation of the v_2(p_T) observed at LHC.Comment: 6 pages, 3 figures, proceedings of the workshop EPIC@LHC, 6-8 July 2011, Bari, Ital

Hadronization via Coalescence

We review the quark coalescence model for hadronization in relativistic heavy ion collisions and show how it can explain the observed large baryon to meson ratio at intermediate transverse momentum and scaling of the elliptic flows of identified hadrons. We also show its predictions on higher-order anisotropic flows and discuss how quark coalescence applied to open- and hidden-charm mesons can give insight to charm quark interactions in the quark-gluon plasma and $J/\Psi$ production in heavy ion collisions.Comment: 6 pages, 4 figures, Proceedings of 20th Winter Workshop on Nuclear Dynamics, Trelawny Beach, Jamaica, March 15--20, 200

Probing the Nuclear Symmetry Energy with Heavy Ion Collisions

Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. In this report we present a selection of new reaction observables in dissipative collisions particularly sensitive to the symmetry term of the nuclear Equation of State ($Iso-EoS$). We will first discuss the Isospin Equilibration Dynamics. At low energies this manifests via the recently observed Dynamical Dipole Radiation, due to a collective neutron-proton oscillation with the symmetry term acting as a restoring force. At higher beam energies Iso-EoS effects will be seen in an Isospin Diffusion mechanism, via Imbalance Ratio Measurements, in particular from correlations to the total kinetic energy loss. For fragmentation reactions in central events we suggest to look at the coupling between isospin distillation and radial flow. In Neck Fragmentation reactions important Iso-EoS information can be obtained from fragment isospin content, velocity and alignement correlations. The high density symmetry term can be probed from isospin effects on heavy ion reactions at relativistic energies (few AGeV range), in particular for high transverse momentum selections of the reaction products. Rather isospin sensitive observables are proposed from nucleon/cluster emissions, collective flows and meson production. The possibility to shed light on the controversial neutron/proton effective mass splitting in asymmetric matter is also suggested. A large symmetry repulsion at high baryon density will also lead to an "earlier" hadron-deconfinement transition in n-rich matter. The binodal transition line of the (T,\rho_B) diagram is lowered to a region accessible through heavy ion collisions in the energy range of the new planned facilities, e.g. the FAIR/NICA projects. Some observable effects of the formation of a Mixed Phase are suggested, in particular a Neutron Trapping mechanism. The dependence of the results on a suitable treatment of the isovector part of the interaction in effective QCD Lagrangian approaches is critically discussed. We stress the interest of this study in nuclear astrophysics, in particular for supernovae explosions and neutron star structure, where the knowledge of the Iso-EoS is important at low as well as at high baryon density.Comment: 52 pages, 28 figures, topical review submitted to J. Phys. G: Nucl. Phys (IOP Latex

Reaction Dynamics with Exotic Beams

We review the new possibilities offered by the reaction dynamics of asymmetric heavy ion collisions, using stable and unstable beams. We show that it represents a rather unique tool to probe regions of highly Asymmetric Nuclear Matter ($ANM$) in compressed as well as dilute phases, and to test the in-medium isovector interaction for high momentum nucleons. The focus is on a detailed study of the symmetry term of the nuclear Equation of State ($EOS$) in regions far away from saturation conditions but always under laboratory controlled conditions. Thermodynamic properties of $ANM$ are surveyed starting from nonrelativistic and relativistic effective interactions. In the relativistic case the role of the isovector scalar $\delta$-meson is stressed. The qualitative new features of the liquid-gas phase transition, "diffusive" instability and isospin distillation, are discussed. The results of ab-initio simulations of n-rich, n-poor, heavy ion collisions, using stochastic isospin dependent transport equations, are analysed as a function of beam energy and centrality. The isospin dynamics plays an important role in all steps of the reaction, from prompt nucleon emissions to the final fragments. The isospin diffusion is also of large interest, due to the interplay of asymmetry and density gradients. In relativistic collisions, the possibility of a direct study of the covariant structure of the effective nucleon interaction is shown. Results are discussed for particle production, collective flows and iso-transparency. Perspectives of further developments of the field, in theory as well as in experiment, are presented.Comment: 167+5 pages, 77 figures, general revie

Isospin in fragment production

Based on a general approach to binary systems we show that in the low density region asymmetric nuclear matter (ANM) is unstable only against isoscalarlike fluctuations. The physical meaning of the thermodynamical chemical and mechanical instabilities is related to the inequality relations verified by the strength of interaction among different components. Relevance of these results in bulk and neck fragmentation is discussed.Comment: 8 pages, 5 Postscript figures, talk at Cortona 2002 Conference, Oct.7-Oct.12, Italy, World Scientific (in press

Impact of temperature dependence of the energy loss on jet quenching observables

The quenching of jets (particles with $p_T>>T, \Lambda_{QCD}$) in ultra-relativistic heavy-ion collisions has been one of the main prediction and discovery at RHIC. We have studied, by a simple jet quenching modeling, the correlation between different observables like the nuclear modification factor \Rapt, the elliptic flow $v_2$ and the ratio of quark to gluon suppression $R_{AA}(quark)/R_{AA}(gluon)$. We show that the relation among these observables is strongly affected by the temperature dependence of the energy loss. In particular the large $v_2$ and and the nearly equal \Rapt of quarks and gluons can be accounted for only if the energy loss occurs mainly around the temperature $T_c$ and the flavour conversion is significant.Finally we point out that the efficency in the conversion of the space eccentricity into the momentum one ($v_2$) results to be quite smaller respect to the one coming from elastic scatterings in a fluid with a viscosity to entropy density ratio $4\pi\eta/s=1$.Comment: 7 pages, 8 figures, Workshop WISH 201