4046382
Nuclear symmetry potential in the relativistic impulse approximation
Using the relativistic impulse approximation with the Love-Franey NN scattering amplitude developed by Murdock and Horowitz, we investigate the low-energy (100{<=}E{sub kin}{<=}400 MeV) behavior of the nucleon Dirac optical potential, the Schroedinger-equivalent potential, and the nuclear symmetry potential in isospin asymmetric nuclear matter. We find that the nuclear symmetry potential at fixed baryon density decreases with increasing nucleon energy. In particular, the nuclear symmetry potential at saturation density changes from positive to negative values at nucleon kinetic energy of about 200 MeV. Furthermore, the obtained energy and density dependence of the nuclear symmetry potential is consistent with those of the isospin- and momentum-dependent MDI interaction with x=0, which has been found to describe reasonably well both the isospin diffusion data from heavy-ion collisions and the empirical neutron-skin thickness of {sup 208}Pb.
121145994
Nuclear matter saturation point and symmetry energy with modern nucleon-nucleon potentials
We determine the saturation properties of nuclear matter within the Brueckner-Hartree-Fock approach based on a large set of modern nucleon-nucleon potentials and confirm the validity of the Coester band. The improvement of the saturation point when including nuclear three-body forces is pointed out and comparison with the Dirac-Brueckner-Hartree-Fock results is made.
122278849
Neutron star structure with modern nucleonic three-body forces
We provide convenient parametrizations of the high-density nuclear equation of state obtained within the Brueckner-Hartree-Fock approach using different modern nucleon-nucleon potentials together with compatible microscopic nuclear three-body forces. The corresponding neutron star mass-radius relations are also presented.
119587623
Consistent nucleon-nucleon potentials and three-body forces
We construct microscopic three-nucleon forces consistent with the Bonn and Nijmegen two-nucleon potentials, and including \ensuremath{\Delta}, Roper, and nucleon-antinucleon excitations. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined.
122221874
Three-body force rearrangement effect on single particle properties in neutron-rich nuclear matter
119441908
Dynamical isospin effects in nucleon-induced reactions
The isospin effects in proton-induced reactions on isotopes of $^{112\ensuremath{-}132}\mathrm{Sn}$ and the corresponding $\ensuremath{\beta}$-stable isobars are studied by means of the improved quantum molecular dynamics model and some sensitive probes for the density dependence of the symmetry energy at subnormal densities are proposed. The beam energy range is chosen to be 100\char21{}300 MeV. Our study shows that the system size dependence of the reaction cross sections for $p+{}^{112\ensuremath{-}132}\mathrm{Sn}$ deviates from the Carlson's empirical expression obtained by fitting the reaction cross sections for proton on nuclei along the $\ensuremath{\beta}$-stability line and sensitively depends on the stiffness of the symmetry energy. We also find that the angular distribution of elastic scattering for $p+{}^{132}\mathrm{Sn}$ at large impact parameters is very sensitive to the density dependence of the symmetry energy, which is uniquely due to the effect of the symmetry potential with no mixture of the effect from the isospin dependence of the nucleon-nucleon cross sections. The isospin effects in neutron-induced reactions are also studied and it is found that the effects are just opposite to that in proton-induced reactions. We find that the difference between the peaks of the angular distributions of elastic scattering for $p+{}^{132}\mathrm{Sn}$ and $n+{}^{132}\mathrm{Sn}$ at ${E}_{p,n}=100$ MeV and $b=7.5$ fm is positive for soft symmetry energy ${U}_{\mathrm{sym}}^{\mathrm{sf}}$ and negative for super-stiff symmetry energy ${U}_{\mathrm{sym}}^{\mathrm{nlin}}$ and close to zero for linear density dependent symmetry energy ${U}_{\mathrm{sym}}^{\mathrm{lin}}$, which seems very useful for constraining the density dependence of the symmetry energy at subnormal densities.
118527020
Nuclear symmetry energy at subnormal densities from measured nuclear masses
The symmetry energy coefficients for nuclei with mass number A = 20-250 are extracted from more than 2000 measured nuclear masses. With the semiempirical connection between the symmetry energy coefficients of finite nuclei and the nuclear symmetry energy at reference densities, we investigate the density dependence of the symmetry energy of nuclear matter at subnormal densities. The obtained results are compared with those extracted from other methods.
119112933
Competition between Coulomb and symmetry potential in semi-peripheral heavy ion collisions
The anisotropy of angular distributions of emitted nucleons and light charged particles for the asymmetric reaction system, $^{40}$Ar+$^{197}$Au, at b=6fm and $E_{beam}$=35, 50 and 100MeV/u, are investigated by using the Improved Quantum Molecular Dynamics model. The competition between the symmetry potential and Coulomb potential shows large impacts on the nucleons and light charged particles emission in projectile and target region. As a result of this competition, the angular distribution anisotropy of coalescence invariant Y(n)/Y(p) ratio at forward regions shows sensitivity to the stiffness of symmetry energy as well as the value of Y(n)/Y(p). This observable can be further checked against experimental data to understand the reaction mechanism and to extract information about the symmetry energy at subsaturation densities.
119107991
Transport model study of nuclear stopping in heavy-ion collisions over the energy range from 0.09A to 160A GeV
Nuclear stopping in heavy-ion collisions over a beam energy range from SIS and AGS up to SPS is studied in the framework of the modified Ultrarelativistic Quantum Molecular Dynamics transport model, in which mean field potentials of both formed and "preformed" hadrons (from string fragmentation) and medium-modified nucleon-nucleon elastic cross sections are considered. It is found that nuclear stopping is influenced by both the stiffness of the equation of state and medium modifications of nucleon-nucleon cross sections at SIS energies. At high SPS energies, a two-bump structure is shown in the experimental rapidity distribution of free protons, which can be understood by considering the preformed hadron potentials.
119339630
Quark model study of the eta photoproduction: Evidence for a new S(11) resonance?
An extensive and systematic study of the recent eta photoproduction data up to 1.2 GeV is presented within a chiral constituent quark model. A model embodying all known nucleonic resonances shows clear need for a yet undiscovered third S11 resonance in the second resonance region, for which we determine the mass (1.729 GeV) and the total width (183 MeV). Furthermore, we extract the configuration mixing angles, an important property of the quark-quark interaction in the quark model, for the resonances S11(1535) and S11(1650), as well as for the resonances D13(1520) and D13(1700). Our results agree well with the quark model predictions. In addition, the partial eta N decay widths and/or the photo-excitation helicity amplitudes for the nucleonic resonances S11(1535), S11(1650), P11(1710), P13(1720), D13(1520), D13(1700), D15(1675), and F15(1680) are also obtained in this approach.