Nuclear Theory·nucl-th

Monday·December 2, 2024

14 papers—9 primary·5 cross-listed

01
[Submitted on 28 Nov 2024]
Enhanced nuclear Schiff and electric dipole moments in nuclei with an octupole deformation
V. V. Flambaum🇦🇺 · A. J. Mansour🇦🇺
Deformed nuclei exhibit enhanced moments that violate time-reversal invariance ( $T$ ) and parity ( $P$ ). This paper focuses on the enhanced nuclear electric dipole moment (EDM) and Schiff moment present in nuclei with octupole deformation (pear-shaped nuclei). These moments, which are proportional to the octupole deformation, have a collective nature and are large in the intrinsic frame that rotates with the nucleus. However, in a state with definite angular momentum and parity, $T$ and $P$ conservation forbid their expectation values in the laboratory frame, as nuclear rotation causes them to vanish. In nuclei with octupole deformation, close opposite-parity rotational states with identical spin are mixed by $T$ , $P$ -violating nuclear forces. This mixing polarises the nuclear axis along the nuclear spin, allowing moments from the intrinsic frame to manifest in the laboratory frame, provided the nuclear spin $I$ is sufficiently large. Using half-life data for $E 1$ transitions from the NuDat database, we calculate the intrinsic nuclear EDM $d_{int}$ for a range of nuclei theorised to exhibit octupole deformation. From these values, we independently estimate the intrinsic nuclear Schiff moment $S_{int}$ and the octupole deformation parameter $β_{3}$ . Finally, we compare the magnitude of these collective moments in the laboratory frame with the contributions from valence nucleons, providing an estimate of the nuclear EDM and Schiff moment components unrelated to octupole deformation. The uncertainty of our estimates may exceed a factor of 10.
Comments:
arXiv admin note: text overlap with arXiv:2302.00214
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Atomic Physics (physics.atom-ph)
arXiv:
2411.18943 [pdf]
PRC(2025)·5 citations
02
[Submitted on 28 Nov 2024]
Elastic properties of nuclear pasta in neutron-star crusts
Cheng-Jun Xia · Toshiki Maruyama · Nobutoshi Yasutake · Toshitaka Tatsumi · Ying-Xun Zhang
Based on the relativistic mean field (RMF) model with Thomas-Fermi approximation, we investigate the elastic properties of neutron star matter. The elastic constants are estimated by introducing deformations on the nuclear pasta structures in $β$ -equilibrium, where various crystalline configurations are considered in a fully three-dimensional geometry without the Wigner-Seitz approximation. Two scenarios with different symmetry energy slope ( $L = 41.34$ and 89.39 MeV) are examined, where the the elastic constants can vary by ten times. By fitting to the numerical results, we improve the analytic formulae for the elastic properties of nuclear pasta by introducing damping factors.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2411.19013 [pdf]
Nucl.Phys.Rev.(2024)·0 citations
03
[Submitted on 28 Nov 2024]
Phase diagrams of neutron-proton superfluid in asymmetric nuclear matter
K. D. Duan · H. B. Zhang · X. L. Shang
The finite-temperature phase structures for neutron-proton superfluidity in asymmetric nuclear matter are investigated, with a particular focus on the angular dependence of the pairing gap induced by the $^{3} S D_{1}$ $N N$ interaction. This angular dependence of the pairing gap results in the Cooper pair momentum in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state exhibiting exactly two distinct stable orientations: one orthogonal (FFLO-ADG-O) and the other parallel (FFLO-ADG-P) to the symmetry axis of the pairing gap. The FFLO-ADG-O state dominates at low asymmetries, while the FFLO-ADG-P state prevails at high asymmetries. Additionally, these analysis of normal-superfluid phase separation reveals that the angular dependence of the pairing gap eliminates phase separation in the low-asymmetry regime, whereas the Cooper pair momentum effectively suppresses phase separation at high asymmetries. These two mechanisms act in concert to significantly prevent the occurrence of normal-superfluid phase separation across the entire phase diagram, ensuring the stability of the homogeneous superfluid state over a broad range of asymmetries. These results provide new insights into the interplay between the angular dependence of the pairing gap and the stability of superfluidity in asymmetric nuclear matter.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.19052 [pdf]
PRC(2025)·4 citations
04
[Submitted on 29 Nov 2024]
Deep learning for nuclear masses in deformed relativistic Hartree-Bogoliubov theory in continuum
Soonchul Choi · Kyungil Kim · Zhenyu He · Youngman Kim · Toshitaka Kajino
Most nuclei are deformed, and these deformations play an important role in various nuclear and astrophysical phenomena. Microscopic nuclear mass models have been developed based on covariant density functional theory to explore exotic nuclear properties. Among these, we adopt mass models based on the relativistic continuum Hartree-Bogoliubov theory (RCHB) with spherical symmetry and the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with axial symmetry to study the effects of deformation on the abundances produced during the rapid neutron-capture process (r-process). Since the DRHBc mass table has so far been completed only for even-Z nuclei, we first investigate whether a Deep Neural Network (DNN) can be used to extend the DRHBc mass table by focusing on nuclear binding energies. To incorporate information about odd-odd and odd-even isotopes into the DNN, we also use binding energies from AME2020 as a training set, in addition to those from the DRHBc mass table for even-Z nuclei. After generating an improved mass table through the DNN study, we conduct a sensitivity analysis of r-process abundances to deformation or mass variations using the RCHB $^{⋆}$ and DRHBc $^{⋆}$ mass tables (where $⋆$ indicates that the mass table is obtained from the DNN study). For the r-process sensitivity study, we consider magnetohydrodynamic jets and collapsar jets. Our findings indicate that r-process abundances are sensitive to nuclear deformation, particularly within the mass range of $A = 80 - 120$ .
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.19470 [pdf]
PRC(2026)·2 citations
05
[Submitted on 29 Nov 2024]
Sensitivity analysis of $β$ -decay half-life predictions for Ge, As, Zr and Mo nuclei within the mapped interacting boson model
M. Homma · K. Nomura
We analyze parameter sensitivities of the mapped interacting boson model (IBM) and boson-fermion-fermion model (IBFFM) in the description of $β$ -decay properties of the even-mass neutron-deficient Ge and As, and neutron-rich Zr and Mo isotopes. Based on the self-consistent mean-field calculations with a given energy density functional and a pairing interaction, the IBM Hamiltonian for even-even nuclei, single-particle energies, and occupation probabilities for unpaired nucleons, which are necessary building blocks of the IBFFM Hamiltonian and Gamow-Teller and Fermi transition operators, are completely determined. A few coupling constants of the boson-fermion and residual neutron-proton interactions are only phenomenological parameters fitted to reproduce low-energy spectra of odd-mass and odd-odd nuclei. It is found that the calculated $lo g_{10} f t$ values for the $β^{+}$ decays $^{68}$ As $\to^{68}$ Ge are particularly sensitive to the quadrupole-quadrupole boson interaction strength used for the parent ( $^{68}$ As) nucleus. We further incorporate higher-order terms in the one-nucleon transfer operators in the boson system, and find that, while their effects are non-negligible, they do not significantly alter qualitative features of $β$ -decay properties. We report a novel application of the mapped IBM framework to compute $β$ -decay half-lives, and show that the observed trend along isotopic chains are reasonably reproduced.
Comments:
18 pages, 13 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2411.19480 [pdf]
PRC(2025)·1 citation
06
[Submitted on 29 Nov 2024]
Non-perturbative three-nucleon simulation using chiral lattice EFT
Lukas Bovermann🇩🇪 · Evgeny Epelbaum🇩🇪 · Hermann Krebs🇩🇪 · Dean Lee🇺🇸
We study the three-nucleon system at next-to-next-to-next-to-leading order ( $N^{3} LO$ ) in the framework of chiral effective field theory (EFT) on the lattice. Our calculations do not rely on a perturbative treatment of subleading contributions to the nuclear forces. For the two-nucleon potential, we apply the previously developed $N^{3} LO$ lattice interaction. For the leading contribution to the three-nucleon force, we determine the two low-energy constants (LECs) in the contact interactions by adjusting the ground state energy and half-life of triton, where the latter employs the nuclear axial current at $N^{2} LO$ in chiral EFT. Additionally, the ground state energy of helion and the charge radii of the two considered nuclei are computed. No effect of the smearing regularization in the three-nucleon contact interaction is observed here. We compare our results with recent lattice-EFT calculations that are based on a potential tuned to light and medium-mass nuclei using the wave-function-matching technique to circumvent the Monte-Carlo sign problem.
Comments:
8 pages, 1 figure, 1 table, to be published in proceedings of the 11th International Workshop on Chiral Dynamics - CD2024
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2411.19613 [pdf]
PoS(2026)·0 citations
07
[Submitted on 29 Nov 2024]
Electromagnetic Probes of the Quantum Chromodynamical Plasma
Gojko Vujanovic🇨🇦
In relativistic heavy-ion collisions, electromagnetic (EM) radiation has been used as a sensitive probe of Quark Gluon Plasma (QGP) properties, owing to the smaller EM coupling relative to QCD coupling. To better understand the constraining power of EM emissions on transport properties of the QGP, a deeper understanding of both the theory and phenomenology of EM signals is required. A selection of recent developments in those two areas of QGP EM probes is discussed, with an outlook on how Bayesian model-to-data comparisons can help further quantify our understanding of QGP transport coefficients.
Comments:
6 pages, Proceedings for the 14th International Conference on Nucleus-Nucleus Collisions (NN2024), Whistler, British Columbia, Canada, August 18-23, 2024
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2411.19868 [pdf]
NPA(2025)·2 citations
08
[Submitted on 29 Nov 2024]
Gravitational form factors of the deuteron
J. Yu. Panteleeva🇩🇪 · E. Epelbaum🇩🇪 · A. M. Gasparyan🇩🇪 · J. Gegelia🇩🇪
The gravitational form factors of the deuteron are calculated in the framework of non-relativistic chiral effective field theory. Non-relativistic reduction of the matrix element of the energy-momentum tensor operator for spin-one systems is worked out, and the gravitational form factors of the deuteron are extracted from the three-point function of the energy-momentum tensor using the LSZ reduction formula. The obtained form factors are compared to results of model calculations available in the literature.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2411.19909 [pdf]
Acta Phys.Polon.B(2025)·5 citations
09
[Submitted on 29 Nov 2024]
Direct local parametrization of nuclear state densities using the back-shifted Bethe formula
C. Özen · Y. Alhassid
Level densities are often parametrized using the back-shifted Bethe formula (BBF) for nuclei that possess experimental data for s-wave neutron resonance average spacings and a complete discrete level sequence at low excitation energies. However, these parametrizations require the additional modeling of the dependence of the spin-cutoff parameter on excitation energy. Here we avoid the need to model the spin distribution of level densities by using the experimental data to parametrize directly the state densities, for which the BBF does not depend on the spin-cutoff parameter. This approach allows for a local parameterization of state densities that is independent of the spin-cutoff parameter. We provide these parameters in a tabulated form for applications in nuclear reaction calculations and for testing microscopic approaches to state densities.
Comments:
12 pages, 3 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2411.19940 [pdf]
NPA(2025)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE