Thu·Jun 6, 2024Thursday·June 6, 2024

1. 01*

   Effects of pairing strength on the nuclear structure and double-$\beta$ decay predictions within the mapped interacting boson model

   Kosuke Nomura🇯🇵

   The low-energy nuclear structure and two-neutrino double-$\beta$ ($2\nu \beta \beta$) decay are studied within the interacting boson model (IBM) that is based on the nuclear energy density functional (EDF). The IBM Hamiltonian describing the initial and final even-even nuclei, and the interacting boson fermion-fermion Hamiltonian producing the intermediate states of the neighboring odd-odd nuclei are determined by the microscopic inputs provided by the self-consistent mean-field (SCMF) calculations employing a relativistic EDF and a separable pairing force. Sensitivities of the low-lying structure and $2\nu \beta \beta$-decay properties to the pairing strength are specifically analyzed. It is shown that the SCMF calculations with decreased and increased pairing strengths lead to quadrupole-quadrupole interaction strengths in the IBM that are, respectively, significantly enhanced and reduced in magnitude. When the increased pairing is adopted, in particular, the energy levels of the excited $0^{+}$ states are lowered, and the predicted $2\nu \beta \beta$-decay nuclear matrix elements (NMEs) increase in magnitude systematically. The mapped IBM employing the increased pairing force generates effective NMEs and half-lives that are in a reasonable agreement with the experimental data for the ${}^{76}$Ge${\to }^{76}$Se, ${}^{82}$Se${\to }^{82}$Kr, and ${}^{100}$Mo${\to }^{100}$Ru decays in particular, whereas the calculation with the standard pairing strength is adequate to provide an overall good description of the effective NMEs in agreement with data.

   ↳ nucl-thnucl-exPRC(2024)·8 citations
2. 02*

   Use of quantality in nuclei and many-body systems

   J.-P. Ebran🇫🇷 · L. Heitz🇫🇷 · E. Khan🇫🇷

   The use of quantality is discussed in the case of nuclei and other many-body systems such as atomic electrons. This dimensionless quantity is known to indicate when a many-body system behaves like a crystal or a quantum liquid. Its role is further analyzed by showing its relation to the scattering length. The emergence of a fundamental lengthscale, the limit radius, is also shown. It corresponds to the hard-core of the nucleon-nucleon interaction in the case of nucleons, and to a value close to the Bohr radius in the case of atomic electrons. The occurrence of a cluster phase in nuclei is analyzed using the quantality through its relation to the localization parameter, allowing for the identification of both the number of nucleons and the density as control parameters for the occurrence of this phase. The relation of the quantality to the magnitude of the interaction also exhibits a third dimensionless parameter, monitoring the magnitude of the spin-orbit effect in finite systems, through the realization of the pseudo-spin symmetry. The impact of quantality on the spin-orbit effect is compared in various many-body systems. The role of quantality in the relative effect of the binding energy and the shell one is also analyzed in nuclei. Finally, additional dimensionless quantities are proposed from the generalization of the quantality. Nuclei are found to be exceptional systems because all their dimensionless quantities are close to the order of unity, at variance with other many-body systems.

   ↳ nucl-thnucl-exPRC(2024)·2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.