67842056
Beyond the relativistic mean-field approximation. III. Collective Hamiltonian in five dimensions
The framework of relativistic energy density functionals is extended to include correlations related to the restoration of broken symmetries and fluctuations of collective variables. A new implementation is developed for the solution of the eigenvalue problem of a five-dimensional collective Hamiltonian for quadrupole vibrational and rotational degrees of freedom, with parameters determined by constrained self-consistent relativistic mean-field calculations for triaxial shapes. The model is tested in a series of illustrative calculations of potential energy surfaces and the resulting collective excitation spectra and transition probabilities of the chain of even-even gadolinium isotopes.
15089471
Gauge invariant electromagnetic two-point function for heavy-light quark systems.
A gauge invariant electromagnetic two-point function, crucial to the investigations of the violation of isospin symmetry, is derived for heavy-light quark systems. Thus QED can be consistently introduced into the QCD sum rule method, which was not previously possible.
101147336
Impedance Computation of Main Components in CSNS/RCS
33315431
Spin structure of nucleons in a quark model with constituent gluons.
120492049
Octupole degree of freedom for nuclei near 152Sm in a reflection-asymmetric relativistic mean-field approach
The potential energy surfaces of even-even isotopes near 152Sm are investigated within the constrained reflection-asymmetric relativistic mean-field approach using parameter sets PK1 and NL3. It is shown that the critical-point candidate nucleus 152Sm marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole deformed ground state in 150Sm to the quadrupole deformed ground state in 154Sm. The important role of the octupole deformation driving pair (?2f7/2, ?1i13/2) is demonstrated based on the components of the single-particle levels near the Fermi surface. In addition, the patterns of both the proton and the neutron octupole deformation driving pairs (?2f7/2, ?1i13/2) and (?2d5/2, ?1h11/2) are investigated.
55936188
Effect of time-odd mean fields on inertial parameters of the quadrupole collective Hamiltonian
Most current implementations of the quadrupole collective Hamiltonian model do not include the contributions of time-odd mean fields to the moments of inertia and mass parameters (Thouless-Valatin dynamical rearrangement contributions). A hybrid model is introduced that allows a quantitative estimate of these contributions to the inertial functions of a five- dimensional collective Hamiltonian based on microscopic energy density functionals. Fully self-consistent constrained relativistic Hartree-Bogoliubov calculations of triaxial energy surfaces in the β−γ plane are used to determine the parameters of an equivalent pairing-plus-quadrupole (P+Q) Hamiltonian. This Hamiltonian is employed in constrained Hartree-Fock- Bogoliubov (CHFB) plus local quasiparticle random-phase approximation (LQRPA) calculation of the deformation- dependent corrections to the Inglis-Belyaev moments of inertia and cranking mass parameters. This hybrid model is used to evaluate the influence of time-odd mean fields on vibrational and rotational collective masses and investigate their effect on the low-energy collective excitation spectra and transition rates of γ-soft Xe and Ba nuclei.
119490772
Constraints on the Density Dependence of the Symmetry Energy
Collisions involving {sup 112}Sn and {sup 124}Sn nuclei have been simulated with the improved quantum molecular dynamics transport model. The results of the calculations reproduce isospin diffusion data from two different observables and the ratios of neutron and proton spectra. By comparing these data to calculations performed over a range of symmetry energies at saturation density and different representations of the density dependence of the symmetry energy, constraints on the density dependence of the symmetry energy at subnormal density are obtained. The results from the present work are compared to constraints put forward in other recent analyses.
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.
120197810
Medium effects on the NN inelastic cross section in relativistic heavy-ion collisions☆
Abstract We derive the explicit expressions for calculating the in-medium NN→N Δ cross section within the relativistic Boltzmann-Uehling-Uhlenbeck approach. All the medium effects on the NN inelastic cross section in relativistic HIC are studied systematically. Numerical results are presented for densities up to three times that of nuclear matter.
117793791
Constraints on nucleon effective mass splitting with heavy ion collisions
Abstract A new version of the improved quantum molecular dynamics model has been developed to include standard Skyrme interactions. Four commonly used Skyrme parameter sets, SLy4, SkI2, SkM* and Gs are adopted in the transport model code to calculate the isospin diffusion observables as well as single and double ratios of transverse emitted nucleons. While isospin diffusion observables are sensitive to the symmetry energy term, they are not very sensitive to the nucleon effective mass splitting parameters in the interactions. Our calculations show that the high energy neutrons and protons and their ratios from reactions at different incident energies provide a robust observable to study the momentum dependence of the symmetry potential which leads to the effective mass splitting. However the sensitivity of effective mass splitting effect on the double n/p yield ratios decreases with increasing beam energy, even though high energy protons and neutrons are produced more abundantly at high beam energy. Our calculations show that the optimum incident energy to study nucleon effective masses is between 100–200 MeV per nucleon.
124926981
Analysis of Collective Flow in High Energy Heavy-Ion Collisions in the Relativistic VUU Approach
We have calculated the collective flow for collisions of by using the relativistic Vlasov-Uehling-Uhlenbeck (VUU) equation based on the QHD-I model of Walecka. The tensitivity of flow characterized by and to mean field and in-medium NN scattering cross section is studied. It is found that the azimuthal correlation function is reduced dramatically after inserting the collision term and then varies very slowly between NN cross sections from to and reaches the minimum at , while the in-plane mean transverse momentum increases slowly all the way from to . The collective flow is very sensitive to the momentum dependence (indicated by the effective mass ) of the mean field and less sensitive to the compression modulus K and the cross sections from to . The numerical results were compared with the experimental data, and we found that the agreement for both and can be reached with the same set of mean field parameters as well as the appropriate NN cross section in collision terms.