8,438 research outputs found
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 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 (). 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 () 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 () in
regions far away from saturation conditions but always under laboratory
controlled conditions.
Thermodynamic properties of are surveyed starting from nonrelativistic
and relativistic effective interactions. In the relativistic case the role of
the isovector scalar -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 ) 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 and the ratio of quark to gluon suppression
. We show that the relation among these
observables is strongly affected by the temperature dependence of the energy
loss. In particular the large and and the nearly equal \Rapt of quarks
and gluons can be accounted for only if the energy loss occurs mainly around
the temperature and the flavour conversion is significant.Finally we
point out that the efficency in the conversion of the space eccentricity into
the momentum one () results to be quite smaller respect to the one coming
from elastic scatterings in a fluid with a viscosity to entropy density ratio
.Comment: 7 pages, 8 figures, Workshop WISH 201
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