Constraining the Symmetry Energy:. a Journey in the Isospin Physics from Coulomb Barrier to Deconfinement (original) (raw)
Related papers
Probing the nuclear symmetry energy with heavy-ion collisions
Journal of Physics G: Nuclear and Particle Physics, 2010
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.
Isospin dynamics in heavy ion collisions: From Coulomb barrier to quark gluon plasma
Progress in Particle and Nuclear Physics, 2009
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 neutronproton oscillation with the symmetry term acting as a restoring force. At higher beam energies Iso-EoS effects will be seen in Imbalance Ratio Measurements, in particular from the correlations with 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 the correlation between isospin content and alignement. The high density symmetry term can be probed from isospin effects on heavy ion reactions at relativistic energies (few AGeV range). 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. A suitable treatment of the isovector interaction in the partonic EoS appears very relevant.
Stopping and isospin equilibration in heavy ion collisions
Physics Letters B, 2004
We investigate the density behaviour of the symmetry energy with respect to isospin equilibration in the combined systems Ru(Zr) + Zr(Ru) at relativistic energies of 0.4 and 1.528 AGeV . The study is performed within a relativistic framework and the contribution of the iso-vector, scalar δ field to the symmetry energy and the isospin dynamics is particularly explored. We find that the isospin mixing depends on the symmetry energy and a stiffer behaviour leads to more transparency. The results are also nicely sensitive to the "fine structure" of the symmetry energy, i.e. to the covariant properties of the isovector meson fields.
Isospin effects in intermediate energy heavy ion collisions
We investigate the density dependence of the symmetry energy in a relativistic description by decomposing the iso-vector mean field into contributions with different Lorentz properties. We find important effects of the iso-vector, scalar delta\deltadelta channel on the density behavior of the symmetry energy. Finite nuclei studies show only moderate effects originating from the virtual delta\deltadelta meson. In heavy ion collisions from Fermi to relativistic energies up to 1−2AGeV1-2 AGeV1−2AGeV one finds important contributions on the dynamics arising from the different treatment of the microscopic Lorentz structure of the symmetry energy. We discuss a variety of possible signals which could set constraints on the still unknown density dependence of the symmetry energy, when experimental data will be available. Examples of such observables are isospin collective flow, threshold production of pions and kaons, isospin equilibration and stopping in asymmetric systems like Au+AuAu+AuAu+Au, Sn+SnSn+SnSn+Sn and Ru(Zr)+Zr(Ru)Ru(Zr)+Zr(Ru)Ru(Zr)+Zr(Ru).
Isospin Diffusion and the Nuclear Symmetry Energy in Heavy Ion Reactions
Physical Review Letters, 2004
Using symmetric 112 Sn 112 Sn, 124 Sn 124 Sn collisions as references, we probe isospin diffusion in peripheral asymmetric 112 Sn 124 Sn, 124 Sn 112 Sn systems at an incident energy of E=A 50 MeV. Isoscaling analyses imply that the quasiprojectile and quasitarget in these collisions do not achieve isospin equilibrium, permitting an assessment of isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical observables, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state.
Probing the nuclear symmetry energy with heavy-ion reactions induced by neutron-rich nuclei
2007
Heavy ion collisions (HIC) have been widely used to extract the parametrization of symmetry energy term of nuclear equation of state as a function of barionic density. HIC in fact are a unique tool in terrestrial laboratories to explore the symmetry energy around the saturation density (ρ 0 = 0.16fm −3) from sub-saturation densities (Fermi energies) towards compressed nuclear matter (ρ > 2 − 3ρ 0) that can be reached at relativistic energies, as a function of different conditions of temperature, mass asymmetry and isospin. One of the main study at present is to reach a coherent description of EOS of asymmetric nuclear matter from heavy ion collisions of stable and exotic nuclei, nuclear structure studies and astrophysical observations. In this work an overview of the current status of the research is shortly reviewed together with new perspectives aimed to reduce the present experimental and theoretical uncertainties.
Probing the Symmetry Energy at High Baryon Density with Heavy Ion Collisions
International Journal of Modern Physics E, 2010
The nuclear symmetry energy at densities above saturation density (ρ0 ~ 0.16fm-3) is poorly constrained theoretically and very few relevant experimental data exist. Its study is possible through Heavy Ion Collisions (HIC) at energies E/A > 200 MeV , particularly with beams of neutron-rich radioactive nuclei. The energy range implies that the momentum dependence of the isospin fields, i.e. the difference of the effective masses on protons and neutrons, also has to be investigated before a safe constraint on E sym (ρ) is possible. We discuss the several observables which have been suggested, like n/p emission and their collective flows and the ratio of meson yields with different isospin projection, π-/π+ and K0/K+. We point out several physical mechanisms that should be included in the theoretical models to allow a direct comparison to the more precise experiments which will be able to distinguish the isospin projection of the detected particles: CSR/Lanzhou, FAIR/GSI, RIBF/RIKEN,...
Physical Review C, 2003
We studied the influence of a momentum dependent interaction in the context of isospin effects on fragmentation and dissipation in intermediate energy heavy ion collisions by using an isospin dependent quantum molecular dynamics model. It is shown that nuclear stopping, the number of nucleons emitted, and the multiplicity of intermediate mass fragments are larger with a momentum dependent interaction than without. In particular, the differences for these observables, when using an isospin dependent in-medium nucleon-nucleon cross section versus an isospin independent one, are also larger at high energies for a momentum dependent interaction than without one. Therefore, momentum dependence enhances the sensitivities of those observables to the isospin effect of the in-medium nucleon-nucleon cross section towards high beam energies.