β-decay rates of neutron-rich Zr and Mo isotopes in the deformed quasiparticle random-phase approximation with realistic interactions

Abstract

The β − -decay rates of neutron-rich Zr and Mo isotopes are investigated within the deformed quasiparticle random-phase approximation with realistic nucleon-nucleon interactions. Axially symmetric deformations are considered in the calculations from a mean-field description of a quasiparticle picture and of both particle-hole and particle-particle excitations. The Brückner G matrix obtained with charge-dependent Bonn nucleon-nucleon forces is employed for residual particle-particle and particle-hole interactions. Contributions from both allowed Gammow-Teller and first-forbidden transitions are calculated and the sensitivity of the calculated results to the particle-particle strength is discussed. The calculated β-decay half-lives show a good agreement with the available experimental data. Moreover, predictions of β-decay half-lives are made for some extremely neutron-rich isotopes, which could be useful for future experiments.

Roles of tensor and isoscalar pairing interactions in β-decay calculations for possible r-process waiting point nuclei with N ~ 82 and 126*

“…The inclusion of the tensor force thus provides simultaneous agreements of decay energies and log values of specific decay channels with proper IS pairing and quenching, which are difficult to achieve without it. Moreover, these results agree well with those obtained by the QRPA with realistic forces [14].…”

“…To understand the effect of tensor force and to adjust the parameter better, detailed studies of β-decay beyond half-lives are needed. As performed in [14], we investigate the detailed decay scheme and compare both decay energies as well as log values (the equivalence of nuclear matrix elements). The decay energies can be compared directly with those from the experiments, while the log value comparison is less straightforward, as there always exists the problem of axial-vector coupling constant ( ) quenching, which has an empirical value of approximately , and its origin is still being debated.…”

“…As pointed out in Ref. [14], the QRPA method is in a sense an approximation to the exact shell model calculations. The calculated peak may be further broadened by multi-phonon effects beyond this approach, and this approximation may introduce an effective quenching in addition to the previous quenching for mentioned above, namely,…”

“…In Refs. [13][14][15][16][17], a residual realistic force was used in both the BCS and QRPA calculation for deformed or spherical nuclei and, with a carefully modified Woods-Saxon potential, the β-decay half life of the observed nuclei could be well reproduced as well as those based on Gogny force [18]. In Refs.…”

Calculation of $β$-decay half-lives with Skyrme Hartree-Fock-Bogoliubov+$pn$-QRPA and isoscalar pairing strengths optimized by a Bayesian method

“…In particular, a self-consistent framework, which means the use of same interaction between the ground and excited states, is considered to be the reasonable approach reducing ambiguities on the interactions. A lot of studies within this framework have been carried out to study the βdecay half-lives for specific isotopic or isotonic chains, e.g., the proton-neutron quasiparticle random-phase approximation (pnQRPA) or finite amplitude method (pnFAM) on the top of the energy-density functional (EDF) [5][6][7][8][9][10][11][12][13][14][15][16], the configuration interaction methods [17][18][19], and the interacting boson model [20]. Among them, from the viewpoint of computational feasibility, the pnQRPA and pnFAM are currently the only methods that have been applied to a systematical predic-tion of β-decay half-lives including the first-forbidden (FF) transitions over the nuclear chart [21,22].…”