A consistent folding model analysis of the ( S = 0, T = 1) charge exchange (p, n) reaction measured with 48 Ca, 90 Zr, 120 Sn, and 208 Pb targets at the proton energies of 35 and 45 MeV is done within a two-channel coupling formalism. The nuclear ground state densities given by the Hartree-Fock-Bogoliubov formalism and the density-dependent CDM3Y6 interaction were used as inputs for the folding calculation of the nucleon optical potential and (p, n) form factor. To have an accurate isospin dependence of the interaction, a complex isovector density dependence of the CDM3Y6 interaction has been carefully calibrated against the microscopic Brueckner-Hartree-Fock calculation by Jeukenne, Lejeune, and Mahaux before being used as folding input. Since the isovector coupling was used to explicitly link the isovector part of the nucleon optical potential to the cross section of the (p, n) reaction exciting the 0 + isobaric analog states in 48 Sc, 90 Nb, 120 Sb, and 208 Bi, the newly parametrized isovector density dependence could be well tested in the folding model analysis of the (p, n) reaction. The isospin-and density-dependent CDM3Y6 interaction was further used in the Hartree-Fock calculation of asymmetric nuclear matter, and a realistic estimation of the nuclear symmetry energy was made.

To investigate the behavior of the N = 14 neutron gap far from stability with a neutron-sensitive probe, proton elastic and 2(1)+ inelastic scattering angular distributions for the neutron-rich nucleus 22O were measured using the MUr à STrip detector array at the Grand Accélérateur National d'Ions Lourds facility. A deformation parameter beta(p,p') = 0.26 +/- 0.04 is obtained for the 2(1)+ state, much lower than in 20O, showing a weak neutron contribution to this state. A microscopic analysis was performed using matter and transition densities generated by continuum Skyrme-Hartree-Fock-Bogoliubov and quasiparticle random phase approximation calculations, respectively. The ratio of neutron to proton contributions to the 2(1)+ state is found close to the N/Z ratio, demonstrating a strong N = 14 shell closure in the vicinity of the neutron drip line.

A consistent folding analysis of the elastic p( 6 He, 6 He)p scattering and charge exchange p( 6 He, 6 Li * )n reaction data measured at E lab = 41.6A MeV has been performed within the coupled channels formalism. We have used the isovector coupling to link the isospin dependence of 6 He+p optical potential to the cross section of p( 6 He, 6 Li * )n reaction exciting the 0 + isobaric analog state (IAS) at 3.563 MeV in 6 Li. Based on these results and the Hartree-Fock calculation of asymmetric nuclear matter using the same isospin-dependent effective nucleon-nucleon interaction, we were able to confirm that the most realistic value of the symmetry energy Esym is around 31 MeV. Our analysis has also shown that the measured charge exchange p( 6 He, 6 Li * )n data are quite sensitive to the halo tail of the 6 He density used in the folding calculation and the IAS of 6 Li is likely to have a halo structure similar to that established for the ground state of 6 He. The knowledge about the symmetry part of the nuclear equation of state (EOS) is vital for the understanding of the dynamics of supernovae explosion and the formation of neutron stars [1,2]. The symmetry part of the nuclear EOS is actually determined by the nuclear matter (NM) symmetry energy S(ρ) defined in terms of a Taylor series expansion of the NM binding energy B(ρ, δ) aswhere δ = (ρ n − ρ p )/ρ is the neutron-proton asymmetry parameter. The contribution of O(δ 4 ) and higher-order terms in Eq. (1), i.e., the deviation from the parabolic law was proven to be negligible [3,4]. The NM symmetry energy determined at the NM saturation density, E sym = S(ρ 0 ) with ρ 0 ≈ 0.17 fm −3 , is widely known in the literature as the symmetry energy or symmetry coefficient. Although numerous nuclear many-body calculations have predicted E sym to be around 30 MeV (see, e.g., Refs. [3,4,5,6,10]), a direct experimental determination of E sym still remains a challenging task. One needs, therefore, to relate E sym to some experimentally inferrable quantity like the neutron skin in neutron-rich nuclei [7,8,9,10] or the fragmentation data of heavy-ion (HI) collisions involving N = Z nuclei [11,12,13]. An accurate estimate of the E sym value is also very important for the nuclear astrophysics. For example, a small variation of E sym , used as input for the hydrodynamic simulation of supernovae, affects significantly the electron capture rate in the "prompt" phase of type II supernovae [2]. Another example is a calculation of NM and masses of finite nuclei using Skyrme forces [6] which shows that the neutron-rich NM does not collapse only if the corresponding E sym value is within the range 28 − 31 MeV. E sym is also an important input for the study of the density dependence S(ρ) based on transport-model simulation of the HI collisions (see Ref.[11] and references * Electronic address: khoa@vaec.gov.vn therein), and the most recent transport-model results favor E sym ≈ 31 − 32 MeV [13].Within the frame of any microscopic model for asymmetric NM, the symmetry energy depends stro...

The two recent density-dependent versions of the finite-range M3Y interaction (CDM3Yn and M3Y-Pn) have been probed against the bulk properties of asymmetric nuclear matter (NM) in the nonrelativistic Hartree Fock (HF) formalism. The same HF study has also been done with the famous Skyrme (SLy4) and Gogny (D1S and D1N) interactions which were well tested in the nuclear structure calculations. Our HF results are compared with those given by other many-body calculations like the Dirac-Brueckner Hartree-Fock approach or ab-initio variational calculation using free nucleon-nucleon interaction, and by both the nonrelativistic and relativistic mean-field studies using different model parameters. Although the two considered density-dependent versions of the M3Y interaction were proven to be quite realistic in the nuclear structure or reaction studies, they give two distinct behaviors of the NM symmetry energy at high densities, like the Asy-soft and Asy-stiff scenarios found earlier with other mean-field interactions. As a consequence, we obtain two different behaviors of the proton fraction in the β-equilibrium which in turn can imply two drastically different mechanisms for the neutron star cooling. While some preference of the Asy-stiff scenario was found based on predictions of the latest microscopic many-body calculations or empirical NM pressure and isospin diffusion data deduced from heavy-ion collisions, a consistent mean-field description of nuclear structure database is more often given by some Asy-soft type interaction like the Gogny or M3Y-Pn ones. Such a dilemma poses an interesting challenge to the modern mean-field approaches.