Nuclear Theory·nucl-th

Tuesday·March 10, 2020

9 papers—5 primary·4 cross-listed

01
Physical features of strength of isoscalar pairing interaction determined by relation between double charge change and double pair transfer
J. Terasaki🇨🇿
A new method has been proposed to determine the strength of the isoscalar proton-neutron pairing interaction applicable to many nuclei. The principle is the equivalence between the double charge change and the double transfer of like-particle pair, and a constraint is derived to the effective interactions used in approximations. This method was applied to the quasiparticle random-phase approximation for determining that interaction strength. In this paper, detail of this method is explained thoroughly, and applications are made to nuclei of several instances of the double- $β$ decays. The systematics of the strengths determined for those nuclei is understood in terms of a midshell effect. The effect of the new interaction strength is examined in two examples of the Gamow-Teller strength function with comparisons with the experimental data. The nuclear matrix elements of the neutrinoless double- $β$ decay are also calculated.
nucl-thnucl-exPRC(2020)·41 citations
02
A microscopic model for spontaneous fission: validity of the adiabatic approximation
K. Hagino · G.F. Bertsch
We investigate microscopically the tunneling dynamics in spontaneous fission of atomic nuclei. To this end, we employ a schematic solvable model with a pairing-plus-quadrupole interaction. The spontaneous decay of a system is simulated by introducing a small imaginary part to the energy of a fission doorway state. We show that the many-body Hamiltonian can be reduced to an effective 2 $\times$ 2 Hamiltonian, from which one can derive a simple approximate formula for the decay width. We particularly investigate the applicability of the adiabatic approximation, which has often been used in the literature. With typical value of the parameters, we find that the adiabatic approximation works within a factor of around 5 for the decay width.
nucl-thPRC(2020)·6 citations
03
Chiral phase transition in a rotating sphere
Zheng Zhang🇨🇳 · Chao Shi🇨🇳 · Xiaofeng Luo🇨🇳 · Hong-Shi Zong🇨🇳
We study the chiral phase transition of the two-flavor Nambu-Jona-Lasinio (NJL) model in a rotating sphere, which includes both rotation and finite size effects. We find that rotation leads to a suppression of the chiral condensate at a finite temperature, while its effects are smaller than the finite size effects. Our work can be helpful to study the effects relevant to rotation in heavy-ion collisions in a more realistic way.
nucl-thPRD(2020)·13 citations
04
Nuclear matrix elements for $λ$ mechanism of $0 ν β β$ of $^{48}$ Ca in nuclear shell-model: Closure versus nonclosure approach
Shahariar Sarkar🇮🇳 · Y. Iwata🇯🇵 · P.K. Raina🇮🇳
The $λ$ and $m_{β β}$ mechanisms of neutrinoless double beta decay ( $0 ν β β$ ) occur with light neutrino exchange via $W_{L} - W_{R}$ , and $W_{L} - W_{L}$ mediation, respectively. In the present study, we calculate the nuclear matrix elements (NMEs) for the $m_{β β}$ and $λ$ mechanisms of $0 ν β β$ , which has origin in the left-right symmetric model with right-handed gauge boson at TeV scale. The NMEs are calculated for one of the $0 ν β β$ decaying isotope $^{48}$ Ca in the interacting nuclear shell-model using the GXPF1A effective interaction of $p f$ -shell. The NMEs are calculated in both closure and nonclosure approaches using four different methods: closure, running closure, running nonclosure, and mixed methods. All the NMEs are calculated incorporating the effects of the finite size of nucleons and the revisited higher order terms such as isoscalar and weak magnetism terms of the nucleon currents. Inclusion of the short-range nature of nucleon-nucleon interaction in Miller-Spencer, CD-Bonn, and AV18 parametrizations is also taken care of. The comparative dependence of the running closure and running nonclosure NMEs with the spin-parity of the allowed states of intermediate nucleus $^{48}$ Sc, the coupled spin-parity of the two initial decaying neutrons and the final two protons, the cutoff excitation energy of $^{48}$ Sc, the cutoff number of states of $^{48}$ Sc are also examined. Results show that there are about 2-20\% enhancements in different types of total NMEs, calculated in the nonclosure approach as compared to the closure approach. The significant enhancements are found in the $M_{q GT}$ and $M_{q T}$ type NMEs for the inclusion of the higher-order terms of the nucleon currents.
nucl-thPRC(2020)·14 citations
05
Effective field theory for triaxially deformed odd-mass nuclei
Q. B. Chen🇩🇪 · N. Kaiser🇩🇪 · Ulf-G. Meißner🇩🇪 · J. Meng🇨🇳
The effective field theory for collective rotations of triaxially deformed nuclei is generalized to odd-mass nuclei by including the angular momentum of the valence nucleon as an additional degree of freedom. The Hamiltonian is constructed up to next-to-leading order within the effective field theory formalism. The applicability of this Hamiltonian is examined by describing the wobbling bands observed in the lutetium isotopes $^{161, 163, 165, 167}$ Lu. It is found that by taking into account the next-to-leading order corrections, quartic in the rotor angular momentum, the wobbling energies $E_{wob}$ and spin-rotational frequency relations $ω (I)$ are better described than with the leading order Hamiltonian.
nucl-thhep-phnucl-ex7 citations

Affiliations

first authorsco-authorsvia INSPIRE

Physical features of strength of isoscalar pairing interaction determined by relation between double charge change and double pair transfer

A microscopic model for spontaneous fission: validity of the adiabatic approximation

Chiral phase transition in a rotating sphere

Nuclear matrix elements for λ mechanism of 0νββ of 48Ca in nuclear shell-model: Closure versus nonclosure approach

Effective field theory for triaxially deformed odd-mass nuclei

Affiliations

Nuclear matrix elements for $λ$ mechanism of $0 ν β β$ of $^{48}$ Ca in nuclear shell-model: Closure versus nonclosure approach