Gao-Chan Yong

Circumstantial evidence for a soft nuclear symmetry energy at suprasaturation densities.

Within an isospin- and momentum-dependent hadronic transport model, it is shown that the recent FOPI data on the pi;{-}/pi;{+} ratio in central heavy-ion collisions at SIS/GSI energies [Willy Reisdorf, Nucl. Phys. A 781, 459 (2007)10.1016/j.nuclphysa.2006.10.085] provide circumstantial evidence suggesting a rather soft nuclear symmetry energy E_{sym}(rho) at rho> or =2rho_{0} compared to the Akmal-Pandharipande-Ravenhall prediction. Some astrophysical implications and the need for further experimental confirmations are discussed.

Near-threshold pion production with radioactive beams

Using an isospin- and momentum-dependent transport model we study near-threshold pion production in heavy-ion collisions induced by radioactive beams at the planned rare isotope accelerator (RIA). We revisit the question of probing the high-density behavior of nuclear symmetry energy E{sub sym}({rho}) using the {pi}{sup -}/{pi}{sup +} ratio. It is found that both the total and differential {pi}{sup -}/{pi}{sup +} ratios remain sensitive to the E{sub sym}({rho}) when the momentum-dependence of both the isoscalar and isovector potentials are consistently taken into account. Moreover, the multiplicity and spectrum of {pi}{sup -} mesons are found more sensitive to the E{sub sym}({rho}) than those of {pi}{sup +} mesons. Finally, effects of the Coulomb potential on the pion spectra and {pi}{sup -}/{pi}{sup +} ratio are also discussed.

Double neutron/proton ratio of nucleon emissions in isotopic reaction systems as a robust probe of nuclear symmetry energy

The double neutron/proton ratio of nucleon emissions taken from two reaction systems using four isotopes of the same element, namely, the neutron/proton ratio in the neutron-rich system over that in the more symmetric system, has the advantage of reducing systematically the influence of the Coulomb force and the normally poor efficiencies of detecting low energy neutrons. The double ratio thus suffers less systematic errors. Within the IBUU04 transport model the double neutron/proton ratio is shown to have about the same sensitivity to the density dependence of nuclear symmetry energy as the single neutron/proton ratio in the neutron-rich system involved. The double neutron/proton ratio is therefore more useful for further constraining the symmetry energy of neutron-rich matter.

Single and double π − / π + ratios in heavy-ion reactions as probes of the high-density behavior of the nuclear symmetry energy

Based on the isospin- and momentum-dependent hadronic transport model IBUU04, effects of the nuclear symmetry energy on the single and double

Double neutron-proton differential transverse flow as a probe for the high density behavior of the nuclear symmetry energy

{\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}

Probing nuclear symmetry energy at high densities using pion, kaon, eta and photon productions in heavy-ion collisions

ratios in central reactions of

Cross-checking the symmetry energy at high densities

^{132}\mathrm{Sn}+^{124}\mathrm{Sn}

Isospin dependence of nucleon emission and radial flow in heavy-ion collisions induced by high energy radioactive beams

and

Effects of pion potential and nuclear symmetry energy on the π-/π+ ratio in heavy-ion collisions at beam energies around the pion production threshold

^{112}\mathrm{Sn}+^{112}\mathrm{Sn}

Model dependence of isospin sensitive observables at high densities

at a beam energy of 400 MeV/nucleon are studied. It is found that around the Coulomb peak of the single