Abstract
A QMD transport model that employs a modified momentum dependent interaction (MDI2) potential, supplemented by a phase-space coalescence model fitted to experimental multiplicities of free nucleons and light clusters, is used to study the density dependence of the symmetry energy above the saturation point by a comparison with experimental elliptic flow ratios measured by the FOPI-LAND and ASYEOS collaborations for 197 Au+197 Au collisions at 400 MeV/nucleon impact energy. Comparing theoretical predictions with experimental data for neutron-to-proton and neutron-to-charged particles elliptic flow ratios the following constraint is extracted for the slope L and curvature Ksym of symmetry energy at saturation: L=59±24(exp)±16(th)±10(sys) MeV and Ksym =0±370(exp)±220(th)±150(sys) MeV. Theoretical errors are the result of poorer known model ingredients. Systematical uncertainties are generated by the inability of the transport model to reproduce experimental light-cluster-to-proton multiplicity ratios. A more accurate value for L , free of systematical theoretical uncertainties, can be extracted from the neutron-to-proton elliptic flow ratio alone: L =63±18(exp)±14(th) MeV.
Highlights
Knowledge of the density dependence of the isospin dependent part of the equation of state of nuclear matter, commonly known as the symmetry energy (SE), is crucial for the understanding of the structure of rare isotopes, dynamics of heavy-ion collisions and properties of astrophysical objects such as neutron stars [1, 2]
A quantum molecular dynamics model (QMD) transport model that employs a modified momentum dependent interaction (MDI2) potential, supplemented by a phase-space coalescence model fitted to experimental multiplicities of free nucleons and light clusters, is used to study the density dependence of the symmetry energy above the saturation point by a comparison with experimental elliptic flow ratios measured by the FOPI-LAND and ASYEOS collaborations for 197Au+197Au collisions at 400 MeV/nucleon impact energy
Comparing theoretical predictions with experimental data for neutron-to-proton and neutron-tocharged particles elliptic flow ratios the following constraint is extracted for the slope L and curvature Ksym of symmetry energy at saturation: L=59±24(exp)±16(th)±10(sys) MeV and Ksym=0±370(exp)±220(th)±150(sys) MeV
Summary
Knowledge of the density dependence of the isospin dependent part of the equation of state (asy-EoS) of nuclear matter, commonly known as the symmetry energy (SE), is crucial for the understanding of the structure of rare isotopes, dynamics of heavy-ion collisions and properties of astrophysical objects such as neutron stars [1, 2]. Constraints for the asy-EoS stiffness have been extracted [7, 9–11] from a comparison of theoretical models with experimental data of the FOPI-LAND [12] and ASYEOS [9] collaborations. [13] had as main goal the extraction of constraints for the slope L and curvature Ksym from the FOPI-LAND npEFR and ASYEOS neutron-to-charged-particles elliptic flow ratio (nchEFR) experimental data. In this conference proceeding the main modifications to the transport model are briefly presented, supplemented by the main results of that study
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