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Nuclear Theory·nucl-th

Thursday·June 3, 2021

11 papers—3 primary·8 cross-listed

All11Primary3Cross-lists8
  1. 01

    Shell effect in 116--124 Tin isotopes investigated using isotopic analysis of proton scattering at 295 MeV

    Yoshiko Kanada-En'yo

    Proton elastic scattering off Sn isotopes at MeV in the mass number range of 116--124 was investigated using calculation employing relativistic impulse approximation (RIA) with theoretical densities obtained for the Sn isotopes from relativistic Hartree-Bogoliubov (RHB) and nonrelativistic Skyrme Hartree-Fock-Bogoliubov (SHFB) calculations of spherical nuclei. In the RIA calculations, a modified version of the Murdock and Horowitz model that includes a density dependence in the effective nucleon-nucleon () interaction was used. A calculation using the theoretical density obtained from a relativistic calculation employing the DD-ME2 interaction successfully reproduced the experimental data for Sn, but it overestimated the Sn and Sn cross sections at backward angles. Isotopic analyses of the reactions combined with nuclear structure properties were performed based on reaction calculations that used a model density modified from the DD-ME2 density to optimize the neutron density of the Sn isotopes by fitting the isotopic cross section ratios. The resulting optimized density reproduced the experimental data for the series of Sn isotopes from Sn to Sn. The neutron root-mean-square(rms) radii and the skin thickness of the Sn isotopes obtained in the present analysis exhibited smooth dependences in the range of 116--124, which are consistent with the theoretical predictions obtained using the DD-ME2 interaction but seem to contradict the experimental results determined from the data. In a detailed analysis of the surface neutron density probed by proton elastic scattering, a signal of the shell effect at in Sn isotopes was found.

    nucl-th1 citation
  2. 02

    Phase-space distributions of nuclear short-range correlations

    W. Cosyn🇺🇸 · J. Ryckebusch🇧🇪

    Nuclear short-range correlations (SRCs) induce high-momentum/high-energy fluctuations in the nuclear medium. In order to assess their impact on nuclear bulk properties, like nuclear radii and kinetic energies, it is instrumental to determine how SRCs are distributed in phase space as this sheds light on the connection between their appearance in coordinate and momentum space. Using the lowest-order correlation operator approximation (LCA) to include SRC, we compute two-dimensional nuclear Wigner quasiprobability distributions to locate those phase-space regions that are most heavily impacted by SRCs. The SRC-induced high-momentum components find their origin in a radial range that is confined to the nuclear interior. Significant SRCs strength is generated in the full momentum range covered in this work, but below the Fermi momentum those are dwarfed by the mean-field contributions. As an application of , we focus on the radial dependence of the kinetic energy and the momentum dependence of the radius for the symmetric nuclei C, Ca and the asymmetric nucleus Ca. The kinetic energy almost doubles after including SRCs, with the largest increase occurring in the nuclear interior fm. The momentum dependence of the teaches that the largest contributions stem from fm, where the SRCs induce a slight reduction of the order of a few percent. The SRCs systematically reduce the Ca neutron skin by an amount that can be 10\%.

    nucl-thnucl-exPLB(2021)·22 citations
  3. 03

    Singular Value Decomposition and Similarity Renormalization Group Evolution of Nuclear Interactions

    B. Zhu · R. Wirth · H. Hergert

    One of the main challenges for ab initio nuclear many-body theory is the growth of computational and storage costs as calculations are extended to heavy, exotic, and structurally complex nuclei. Here, we investigate the factorization of nuclear interactions as a means to address this issue. We perform Singular Value Decompositions of nucleon-nucleon interactions in partial wave representation and study the dependence of the singular value spectrum on interaction characteristics like regularization scheme and resolution scales. We develop and implement the Similarity Renormalization Group (SRG) evolution of the factorized interaction, and demonstrate that this SVD-SRG approach accurately preserves two-nucleon observables. We find that low-resolution interactions allow the truncation of the SVD at low rank, and that a small number of relevant components is sufficient to capture the nuclear interaction and perform an accurate SRG evolution, while the Coulomb interaction requires special consideration. The rank is uniform across all partial waves, and almost independent of the basis choice in the tested cases. This suggests an interpretation of the relevant singular components as mere representations of a small set of abstract operators that can describe the interaction and its SRG flow. Following the traditional workflow for nuclear interactions, we discuss how the transformation between the center-of-mass and laboratory frames creates redundant copies of the partial wave components when implemented in matrix representation, and we discuss strategies for mitigation. Finally, we test the low-rank approximation to the SRG-evolved interactions in many-body calculations using the In-Medium SRG. By including nuclear radii in our analysis, we verify that the implementation of the SRG using the singular vectors of the interaction does not spoil the evolution of other observables.

    nucl-thPRC(2021)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE