Density-dependent NN Interaction Research Articles

Calculations of the Alpha Decay Half-lives of Some Polonium Isotopes Using the Double Folding Model

The calculations of the alpha decay half-lives of some Polonium isotopes in the mass range 186 - 218 have been carried out using the Wentzel-Kramers-Brillouin (WKB) semiclassical approximation. The alpha-nucleus effective potential used contains the Coulomb potential, centrifugal potential, and the nuclear potential. The nuclear potential is obtained via the double folding model, with the microscopic NN effective interactions derived from relativistic mean field theory Lagrangian (termed R3Y). Different parametrizations of the R3Y interactions have been employed in the computation of the nuclear potentials. The results obtained using the R3Y NN interactions are compared with the ones obtained using the famous Michigan-3-Yukawa (M3Y) interactions. The use of density-dependent NN interaction is also considered. When compared to available experimental data, there are improvements in the results when density-dependent interaction potentials are used compared to when density-independent interactions are employed.

Density-dependent NN interaction from subsubleading chiral 3N forces: Intermediate-range contributions

From the subsubleading chiral three-nucleon force [intermediate-range contributions, published in Phys. Rev. C\,87, 054007 (2013)] a density-dependent NN-interaction $V_\text{med}$ is derived in isospin-symmetric nuclear matter. Following the division of the pertinent 3N-diagrams into two-pion-one-pion exchange topology and ring topology, one evaluates for these all selfclosings and concatenations of nucleon-lines to an in-medium loop. In the case of the $2\pi 1\pi$-exchange topology, the momentum- and $k_f$-dependent potentials associated with the isospin-operators ($1$ and $\vec\tau_1 \!\cdot\! \vec\tau_2$) and five independent spin-structures require at most one numerical integration. For the more challenging (concatenations of the) ring diagrams proportional to $c_{1,2,3,4}$, one ends up with regularized double-integrals $\int_0^\lambda dr\,r \int_0^{\pi/2} d\psi$ from which the $\lambda^2$-divergence has been subtracted and the logarithmic piece $\sim \ln (m_\pi/\lambda)$ is isolated. The derived semi-analytical results are most helpful to implement the subsubleading chiral 3N-forces into nuclear many-body calculations.

Spectroscopic factors for alpha decay in the [formula omitted] scheme

Lifetime values for alpha decay in even–even nuclei with Z=84–98 and N=128–152 have been calculated in the superasymmetric fission model. The interaction between the alpha particle and the daughter nucleus has been formed in the double folding approach using a density dependent NN interaction. The densities have been obtained using the Relativistic Mean Field formalism. The spectroscopic factors for the decays have been deduced and are shown to vary smoothly as a function of effective numbers of valence nucleons, Np and Nn chosen with a suitable core. The implication of such a smooth behaviour has been discussed.

The deformation and orientation effect on reaction cross section with deformed targets

The reaction cross section (σR) for a deformed target nucleus and spherical projectile is calculated using the optical-limit approximation of the Glauber-Sitenko theory. A method is presented to include both the density-dependent NN interaction and the higher order deformations of the target nucleus in the collision process. We studied both the orientation and the deformation dependence of σR within the energy range 30–900 MeV/A. We found that the orientation of the heavy target nucleus (A ≥ 120) can produce a difference in the calculated σR up to 30%. The averaged σR over all directions of the symmetry axis of the deformed nucleus differs by less than 1% compared with σR calculated for a spherical target with the same rms matter radius as the deformed nucleus. For certain orientation, it was found that σR is highly dependent on the hexadecapole deformation. The orientation-averaged cross sections show almost no variation with either the sign or the value of the hexadecapole deformation. We compared the average cross section with the experimental data for several mass numbers; fair agreement is obtained.

Relativistic RPA response functions for quasielastic electron scattering with a density-dependent NN interaction

Abstract The longitudinal and transverse response functions as well as the Coulomb sum for quasielastic electron scattering on 12C, 40Ca, 48Ca, 56Fe and 208Pb have been calculated taking into account relativistic RPA correlations. For these calculations a density-dependent relativistic NN interaction reproducing the saturation curve of a Dirac-Brueckner calculation providing a good description of nuclear matter has been used. The agreement with experiment is considerably improved for nuclei ranging from 40Ca to 208Pb, but not for a relatively light nucleus like 12C.