The β-decay half-lives of neutron-rich nuclei with 20 Z 50 are systematically investigated using the newly developed fully self-consistent proton-neutron quasiparticle random phase approximation (QRPA), based on the spherical relativistic Hartree-Fock-Bogoliubov (RHFB) framework. Available data are reproduced by including an isospin-dependent proton-neutron pairing interaction in the isoscalar channel of the RHFB+QRPA model. With the calculated β-decay half-lives of neutron-rich nuclei a remarkable speeding up of r-matter flow is predicted. This leads to enhanced r-process abundances of elements with A 140, an important result for the understanding of the origin of heavy elements in the universe.

We formulate the finite-temperature relativistic Hartree-Bogoliubov theory for spherical nuclei based on a point-coupling functional, with the Gogny or separable pairing force. Using the functional PC-PK1, the framework is applied to the study of pairing transitions in Ca, Ni, Sn, and Pb isotopic chains. The separable pairing force reproduces the gaps calculated with the Gogny force not only at zero temperature, but also at finite temperatures. By performing a systematic calculation of the even-even Ca, Ni, Sn, and Pb isotopes, it is found that the critical temperature for a pairing transition generally follows the rule T c = 0.6∆ n (0), where ∆ n (0) is the neutron pairing gap at zero temperature. This rule is further verified by adjusting the pairing gap at zero temperature with a strength parameter.

The relativistic mean field (RMF) model has achieved great success in describing various nuclear phenomena. However, several serious defects are common. For instance, the pseudo-spin symmetry of high-l orbits is distinctly violated in general, leading to spurious shell closures and . This leads to problems in describing structure properties, including shell structures, nuclear masses, etc. Guided by the pseudo-spin symmetry restoration [Geng et al., Phys. Rev. C, 100: 051301 (2019)], a new RMF Lagrangian DD-LZ1 is developed by considering the density-dependent meson-nucleon coupling strengths. With the newly obtained RMF Lagrangian DD-LZ1, satisfactory descriptions can be obtained for the bulk properties of nuclear matter and finite nuclei. In particular, significant improvements on describing the single-particle spectra are achieved by DD-LZ1. In particular, the spurious shell closures and , commonly found in previous RMF calculations, are eliminated by the new effective interaction DD-LZ1, and consistently the pseudo-spin symmetry (PSS) around the Fermi levels is reasonably restored for both low-l and high-l orbits. Moreover, the description of nuclear masses is also notably improved by DD-LZ1, as compared to the other RMF Lagrangians.

Abstract. Density Functional Theory (DFT) is a powerful and accurate tool exploited in Nuclear Physics to investigate the ground-state and some collective properties of nuclei along the whole nuclear chart. Models based on DFT are, however, not suitable for the description of single-particle dynamics in nuclei. Following the field theoretical approach by A. Bohr and B. R. Mottelson to describe nuclear interactions between single-particle and vibrational degrees of freedom, we have undertaken important steps to build a microscopic dynamic nuclear model. In connection to that, one important issue that needs to be better understood is the renormalization of the effective interaction in the particle-vibration approach. One possible way to renormalize the interaction is the so called subtraction method. In this contribution we will implement the subtraction method for the first time in our model and study its consequences.

The self-consistent quasiparticle random-phase approximation (QRPA) approach is formulated in the canonical single-nucleon basis of the relativistic Hatree-Fock-Bogoliubov (RHFB) theory.This approach is applied to study the isobaric analog states (IAS) and Gamov-Teller resonances (GTR) by taking Sn isotopes as examples. It is found that self-consistent treatment of the particleparticle residual interaction is essential to concentrate the IAS in a single peak for open-shell nuclei and the Coulomb exchange term is very important to predict the IAS energies. For the GTR, the isovector pairing can increase the calculated GTR energy, while the isoscalar pairing has an important influence on the low-lying tail of the GT transition. Furthermore, the QRPA approach is employed to predict nuclear β-decay half-lives. With an isospin-dependent pairing interaction in the isoscalar channel, the RHFB+QRPA approach almost completely reproduces the experimental β-decay half-lives for nuclei up to the Sn isotopes with half-lives smaller than one second. Large discrepancies are found for the Ni, Zn, and Ge isotopes with neutron number smaller than 50, as well as the Sn isotopes with neutron number smaller than 82. The potential reasons for these discrepancies are discussed in detail.

Nuclear β decay in magic nuclei is investigated, taking into account the coupling between particles and collective vibrations, on top of self-consistent random phase approximation calculations based on Skyrme density functionals. The low-lying Gamow-Teller strength is shifted downwards and at times becomes fragmented; as a consequence, the β-decay half-lives are reduced due to the increase of the phase space available for the decay. In some cases, this leads to a very good agreement between theoretical and experimental lifetimes: this happens, in particular, in the case of the Skyrme force SkM* that can also reproduce the line shape of the high-energy Gamow-Teller resonance as was previously shown.

The radial basis function (RBF) approach is applied in predicting nuclear masses for 8 widely used nuclear mass models, ranging from macroscopic-microscopic to microscopic types. A significantly improved accuracy in computing nuclear masses is obtained, and the corresponding rms deviations with respect to the known masses is reduced by up to 78%. Moreover, strong correlations are found between a target nucleus and the reference nuclei within about three unit in distance, which play critical roles in improving nuclear mass predictions. Based on the latest Weizs\"{a}cker-Skyrme mass model, the RBF approach can achieve an accuracy comparable with the extrapolation method used in atomic mass evaluation. In addition, the necessity of new high-precision experimental data to improve the mass predictions with the RBF approach is emphasized as well.Comment: 18 pages, 8 figure

Self-consistent proton-neutron quasiparticle random phase approximation based on the spherical nonlinear point-coupling relativistic Hartree-Bogoliubov theory is established and used to investigate the β + /electroncapture (EC)-decay half-lives of neutron-deficient Ar, Ca, Ti, Fe, Ni, Zn, Cd, and Sn isotopes. The isoscalar proton-neutron pairing is found to play an important role in reducing the decay half-lives, which is consistent with the same mechanism in the β decays of neutron-rich nuclei. The experimental β + /EC-decay half-lives can be well reproduced by a universal isoscalar proton-neutron pairing strength.Nuclear β decays play important roles in many subjects of nuclear physics. Specifically, the investigation of β decay provides information on the spin and isospin dependence of the effective nuclear interaction, as well as on nuclear properties such as masses [1], shapes [2], and energy levels [3]. Moreover, nuclear β decays are also important in nuclear astrophysics, because they set the time scale of the rapid neutron-capture process (r-process) [4][5][6][7][8], which is a major mechanism for producing the elements heavier than iron. In addition, nuclear β decays can provide tests for the electroweak standard model [9][10][11]. With the development of radioactive ion beam facilities, the measurement of nuclear β-decay half-lives has achieved great progress in recent years [12][13][14][15].On the theoretical side, apart from the macroscopic gross theory [16], two different microscopic approaches have been widely used to describe and predict the nuclear β-decay rates. They are the shell model [5] and the proton-neutron quasiparticle random phase approximation (QRPA) [17][18][19]. While the shell model takes into account the detailed structure of the β-strength function, the proton-neutron QRPA approach provides a systematic description of β-decay properties of arbitrarily heavy nuclei. In order to reliably predict properties of thousands of unknown nuclei relevant to the r-process, the self-consistent QRPA approach has become a current trend in nuclear structure study, including those based on the Skyrme-Hartree-Fock-Bogoliubov (SHFB) theory [20] and the covariant density functional theory (CDFT) [21][22][23].In the CDFT framework, the self-consistent proton-neutron RPA was first developed based on the meson-exchange relativistic Hartree (RH) approach [24]. To describe the spinisospin excitations in open shell nuclei, it has been extended to the QRPA based on the relativistic Hartree-Bogoliubov (RHB) approach [25] and employed to calculate the β-decay half-lives of neutron-rich nuclei in the N ≈ 50 and N ≈ 82 regions [21,22]. In addition, based on the meson-exchange * haozhao.liang@riken.jp relativistic Hartree-Fock (RHF) approach [26,27], the selfconsistent proton-neutron RPA has been formulated [28] and well reproduces the spin-isospin excitations in doubly magic nuclei, without any readjustment of the parameters of the covariant energy density functional [28,29]. Recently, the self-consistent QRPA b...