Nuclear Theory·nucl-th

Monday·March 1, 2021

9 papers—5 primary·4 cross-listed

01
[Submitted on 26 Feb 2021]
Jost function formalism with complex potential
K. Mizuyama · T. Dieu Thuy · N. Hoang Tung · D. Quang Tam · T. V. Nhan Hao
The Jost function formalism is extended with use of the complex potential in this paper. We derive the Jost function by taking into account the dual state which is defined by the complex conjugate the complex Hamiltonian. By using the unitarity of the S-matrix which is defined by the Jost function, the optical theorem with the complex potential is also derived. The role of the imaginary part of the complex potential for both the bound states and the scattering states is figured out. The numerical calculation is performed by using the complex Woods-Saxon potential, and some numerical results are demonstrated to confirmed the properties of extended Jost function formalism.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2102.13328 [pdf]
0 citations
02
[Submitted on 26 Feb 2021]
Gamow-Teller transitions of neutron-rich $N = 82, 81$ nuclei by shell-model calculations
Noritaka Shimizu🇯🇵 · Tomoaki Togashi🇯🇵 · Yutaka Utsuno🇯🇵
$β$ -decay half-lives of neutron-rich nuclei around $N = 82$ are key data to understand the $r$ -process nucleosynthesis. We performed large-scale shell-model calculations in this region using a newly constructed shell-model Hamiltonian, and successfully described the low-lying spectra and half-lives of neutron-rich $N = 82$ and $N = 81$ isotones with $Z = 42 - 49$ in a unified way. We found that their Gamow-Teller strength distributions have a peak in the low-excitation energies, which significantly contributes to the half-lives. This peak, dominated by $ν 0 g_{7/2} \to π 0 g_{9/2}$ transitions, is enhanced on the proton deficient side because the Pauli-blocking effect caused by occupying the valence proton $0 g_{9/2}$ orbit is weakened.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2102.13361 [pdf]
PTEP(2021)·7 citations
03
[Submitted on 26 Feb 2021]
Perturbative treatment of three-nucleon force contact terms in three-nucleon Faddeev equations
H. Witała🇵🇱 · J. Golak🇵🇱 · R. Skibiński🇵🇱 · K. Topolnicki🇵🇱
We present a perturbative approach to solving the three-nucleon continuum Faddeev equation. This approach is particularly well suited to dealing with variable strengths of contact terms in a chiral three-nucleon force. We use examples of observables in the elastic nucleon-deuteron scattering as well as in the deuteron breakup reaction to demonstrate high precision of the proposed procedure and its capability to reproduce exact results. A significant reduction of computer time achieved by the perturbative approach in comparison to exact treatment makes this approach valuable for fine-tuning of the three-nucleon Hamiltonian parameters.
Comments:
13 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2102.13408 [pdf]
Few Body Syst.(2021)·9 citations
04
[Submitted on 26 Feb 2021]
Efimov Physics and Connections to Nuclear Physics
A. Kievsky🇮🇹 · L. Girlanda🇮🇹 · M. Gattobigio🇫🇷 · M. Viviani🇮🇹
Physical systems characterized by a shallow two-body bound or virtual state are governed at large distances by a continuous-scale invariance, which is broken to a discrete one when three or more particles come into play. This symmetry induces a universal behavior for different systems, independent of the details of the underlying interaction, rooted in the smallness of the ratio $ℓ / a_{B} ≪ 1$ , where the length $a_{B}$ is associated to the binding energy of the two-body system $E_{2} = ℏ^{2} / m a_{B}^{2}$ and $ℓ$ is the natural length given by the interaction range. Efimov physics refers to this universal behavior, which is often hidden by the on-set of system-specific non-universal effects. In this work we identify universal properties by providing an explicit link of physical systems to their unitary limit, in which $a_{B} \to \infty$ , and show that nuclear systems belong to this class of universality.
Comments:
27 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
arXiv:
2102.13504 [pdf]
Ann.Rev.Nucl.Part.Sci.(2021)·47 citations
05
[Submitted on 26 Feb 2021]
Microscopic analysis of low-energy spin and orbital magnetic dipole excitations in deformed nuclei
V.O. Nesterenko · P.I. Vishnevskiy · J. Kvasil · A. Repko · W. Kleinig
A low-energy magnetic dipole $(M 1)$ spin-scissors resonance (SSR) located just below the ordinary orbital scissors resonance (OSR) was recently predicted in deformed nuclei within the Wigner Function Moments (WFM) approach. We analyze this prediction using fully self-consistent Skyrme Quasiparticle Random Phase Approximation (QRPA) method. Skyrme forces SkM*, SVbas and SG2 are implemented to explore SSR and OSR in $^{160, 162, 164}$ Dy and $^{232}$ Th. Accuracy of the method is justified by a good description of M1 spin-flip giant resonance. The calculations show that isotopes $^{160, 162, 164}$ Dy indeed have at 1.5-2.4 MeV (below OSR) $I^{π} K = 1^{+} 1$ states with a large $M 1$ spin strength ( $K$ is the projection of the total nuclear moment to the symmetry z-axis). These states are almost fully exhausted by $pp [411 ↑, 411 ↓]$ and $nn [521 ↑, 521 ↓]$ spin-flip configurations corresponding to $pp [2 d_{3/2}, 2 d_{5/2}]$ and $nn [2 f_{5/2}, 2 f_{7/2}]$ structures in the spherical limit. So the predicted SSR is actually reduced to low-orbital (l=2,3) spin-flip states. Following our analysis and in contradiction with WFM spin-scissors picture, deformation is not the principle origin of the low-energy spin $M 1$ states but only a factor affecting their features. The spin and orbital strengths are generally mixed and exhibit the interference: weak destructive in SSR range and strong constructive in OSR range. In $^{232}$ Th, the $M 1$ spin strength is found very small. Two groups of $I^{π} = 1^{+}$ states observed experimentally at 2.4-4 MeV in $^{160, 162, 164}$ Dy and at 2-4 MeV in $^{232}$ Th are mainly explained by fragmentation of the orbital strength. Distributions of nuclear currents in QRPA states partly correspond to the isovector orbital-scissors flow but not to spin-scissors one.
Comments:
15 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2102.13580 [pdf]
PRC(2021)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE

Jost function formalism with complex potential

Gamow-Teller transitions of neutron-rich N=82,81 nuclei by shell-model calculations

Perturbative treatment of three-nucleon force contact terms in three-nucleon Faddeev equations

Efimov Physics and Connections to Nuclear Physics

Microscopic analysis of low-energy spin and orbital magnetic dipole excitations in deformed nuclei

Affiliations

Gamow-Teller transitions of neutron-rich $N = 82, 81$ nuclei by shell-model calculations