Nuclear Theory·nucl-th

Tuesday·January 11, 2022

14 papers—10 primary·4 cross-listed

01
[Submitted on 8 Jan 2022]
Microscopic Theory of Nuclear Fission
Nicolas Schunck
Nuclear fission represents the ultimate test for microscopic theories of nuclear structure and reactions. Fission is a large-amplitude, time-dependent phenomenon taking place in a self-bound, strongly-interacting many-body system. It should, at least in principle, emerge from the complex interactions of nucleons within the nucleus. The goal of microscopic theories is to build a consistent and predictive theory of nuclear fission by using as only ingredients protons and neutrons, nuclear forces and quantum many-body methods. Thanks to a constant increase in computing power, such a goal has never seemed more within reach. This chapter gives an overview both of the set of techniques used in microscopic theory to describe the fission process and of some recent successes achieved by this class of methods.
Comments:
37 pages, 8 figures; chapter for the upcoming Handbook in Nuclear Physics edited by I. Tanihata, H. Toki and T. Kajino
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.02716 [pdf]
Tanihata, I., Toki, H., Kajino, T. (eds) …·0 citations
02
[Submitted on 8 Jan 2022]
Theory of Nuclear Fission
Nicolas Schunck🇺🇸 · David Regnier🇫🇷
Atomic nuclei are quantum many-body systems of protons and neutrons held together by strong nuclear forces. Under the proper conditions, nuclei can break into two (sometimes three) fragments which will subsequently decay by emitting particles. This phenomenon is called nuclear fission. Since different fission events may produce different fragmentations, the end-products of all fissions that occurred in a small chemical sample of matter comprise hundreds of different isotopes, including $α$ particles, together with a large number of emitted neutrons, photons, electrons and antineutrinos. The extraordinary complexity of this process, which happens at length scales of the order of a femtometer, mostly takes less than a femtosecond but is not completely over until all the lingering $β$ decays have completed - which can take years - is a fascinating window into the physics of atomic nuclei. While fission may be more naturally known in the context of its technological applications, it also plays a pivotal role in the synthesis of heavy elements in astrophysical environments. In both cases, experimental measurements are not sufficient to provide complete data. Simulations are needed, yet at levels of accuracy and precision that pose formidable challenges to nuclear theory. The goal of this article is to provide a comprehensive overview of the theoretical methods employed in the description of nuclear fission.
Comments:
106 pages, 28 figures, 1 table, 513 references; submitted for publication in Progress in Nuclear and Particle Physics
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.02719 [pdf]
PPNP(2022)·94 citations
03
[Submitted on 8 Jan 2022]
Beta-delayed fission in the coupled Quasi-particle Random Phase Approximation plus Hauser-Feshbach approach
M. R. Mumpower · T. Kawano · T. M. Sprouse
Beta-delayed neutron emission and $β$ -delayed fission ( $β$ df) probabilities were calculated for heavy, neutron-rich nuclei using the Los Alamos coupled Quasi-Particle Random Phase Approximation plus Hauser-Feshbach (QRPA+HF) approach. In this model, the compound nucleus is initially populated by $β$ -decay and is followed through subsequent statistical decays taking into account competition between neutrons, $γ$ -rays and fission. The primary output of these calculations includes branching ratios along with neutron and $γ$ -ray spectra. We find a relatively large region of heavy nuclides where the probability of $β$ df is near 100%. For a subset of nuclei near the neutron dripline, delayed neutron emission and the probability to fission are both large which leads to the possibility of multi-chance $β$ df (mc- $β$ df). We comment on prospective neutron-rich nuclei that could be probed by future experimental campaigns and provide a full table of branching ratios in ASCII format in the supplemental material for use in various applications.
Comments:
12 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2201.02889 [pdf]
PRC(2022)·15 citations
04
[Submitted on 9 Jan 2022]
Properties of Gamow-Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell parent nuclei: a semi-microscopic description
V.I. Bondarenko · M.H. Urin
The basic version of the semi-microscopic particle-hole dispersive optical model is implemented to describe main properties of the Gamow-Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell parent nuclei. Calculation results obtained for $^{48} C a$ , $^{90} Z r$ , $^{132} S n$ , and $^{208} P b$ are compared with available experimental data.
Comments:
26 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.02965 [pdf]
PRC(2022)·5 citations
05
[Submitted on 9 Jan 2022]
Phase-space consideration on barrier transmission in a time-dependent variational approach with superposed wave packets
Akira Ono
A known limitation of time-dependent mean-field approaches is a lack of quantum tunneling for collective motions such as in sub-barrier fusion reactions. As a first step toward a solution, a time-dependent model is considered using a superposition of Gaussian wave packets, to describe the relative motion between two colliding nuclei, which may be simplified to a problem for one particle in one dimension. In this article, how the model describes the potential-barrier transmission is investigated by paying attention to the time evolution of the phase space distribution, which in particular reveals that the behavior of the free propagation of the incoming state is not trivial, depending on the number of superposed wave packets. Passage over the barrier can occur due to the high-momentum components in the incoming state corresponding to energies above the barrier height, which is, however, of classical nature and needs to be distinguished from the true quantum tunneling. Although a transmitted wave packet in some case may end up with an energy lower than the barrier, a difficulty is noticed in guaranteeing the energy conservation when the energies of different exit channels, e.g. of transmission and reflection, are individually measured. To overcome these issues for a description of quantum tunneling is still a challenging problem. This article mainly treats the same system with the same model as in the paper Phys. Lett. B 808 (2020) 135693, arXiv:2006.06944v1 by N. Hasegawa, K. Hagino and Y. Tanimura. However, the conclusion of the present work disagrees with their quick conclusion that quantum tunneling was simulated by the model. Comments are made on this.
Comments:
7 pages, 4 figures, includes comments on arXiv:2006.06944
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.02966 [pdf]
PLB(2022)·5 citations
06
[Submitted on 9 Jan 2022]
Quantum statistical fluctuation of energy and its novel pseudo-gauge dependence
Arpan Das🇵🇱
We discuss the quantum statistical fluctuations of energy in subsystems of hot relativistic gas for both spin-zero and spin half particles. We explicitly show the system size dependence of the quantum statistical fluctuation of energy. Our results show that with decreasing system size quantum statistical fluctuations increase substantially. As the consistency of the framework, we also argue that the quantum statistical fluctuations give rise to the known result for statistical fluctuation of energy in the canonical ensemble if we consider the size of the subsystem to be sufficiently large. For a spin-half particle quantum fluctuations show some interesting novel features. We show that within a small sub-system quantum statistical fluctuation of energy for spin half particles depends on the various pseudo-gauge choices of the energy-momentum tensor. Interestingly, for sufficiently large subsystems quantum fluctuations obtained for different pseudo-gauge choices converge and we recover the canonical-ensemble formula known for statistical fluctuations of energy. Our calculation is very general and can be applied to any branch of physics whenever one deals with a thermal system. As a practical application, we argue that our results can be used to determine a coarse-graining scale to introduce the concept of classical energy density or fluid element relevant for the strongly interacting matter, in particular for small systems produced in heavy-ion collisions.
Comments:
16 pages, 5 captioned figures, Contribution to: 10th International Conference on New Frontiers in Physics (ICNFP 2021)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2201.03011 [pdf]
Phys.Scripta(2022)·0 citations
07
[Submitted on 10 Jan 2022]
Moments and Radii of exotic Na and Mg isotopes
Takaharu Otsuka · Noritaka Shimizu · Yusuke Tsunoda
The ground-state properties of neutron-rich exotic Na and Mg isotopes with even numbers of neutrons, N, are studied up to driplines. The shell-model calculations with an ab initio effective nucleon-nucleon interaction reported in [Tsunoda, Otsuka, Takayanagi et al., Nature 587, 66 (2020)] are extended to observables such as magnetic dipole and electric quadrupole moments, and charge and matter radii. Good agreements with experimental data are found, and predictions are shown up to driplines. A prescription to extract the deformation parameters for the eigenstates of Monte Carlo Shell Model is presented, and the obtained values are used to calculate charge and matter radii. The increase of these radii from the Droplet model is described as the consequences of the varying deformation of the surface and the growing neutron excitations or occupations in the pf shell, consistently with the dripline mechanism presented in the above reference. The neutron skin thickness is shown to be about 0.1 fm for N=20, which can be compared to the value for 208Pb in an A1/3 scaling. The relation of the neutron skin thickness to the electromagnetic moments is discussed for an exotic nucleus, 31Na.
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2201.03190 [pdf]
PRC(2022)·16 citations
08
[Submitted on 10 Jan 2022]
Nuclear mass table in deformed relativistic Hartree-Bogoliubov theory in continuum: I. even-even nuclei
DRHBc Mass Table Collaboration: Kaiyuan Zhang🇨🇳 · Myung-Ki Cheoun🇰🇷 · Yong-Beom Choi🇰🇷 · Pooi Seong Chong🇨🇳 · Jianmin Dong🇨🇳 · Zihao Dong🇨🇳 · Xiaokai Du🇨🇳 · Lisheng Geng🇨🇳 · Eunja Ha🇰🇷 · Xiao-Tao He🇨🇳 · Chan Heo🇨🇳 · Meng Chit Ho🇨🇳 and 34 other authors
Ground-state properties of even-even nuclei with $8 \leq Z \leq 120$ from the proton drip line to the neutron drip line have been investigated using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the density functional PC-PK1. With the effects of deformation and continuum included simultaneously, 2583 even-even nuclei are predicted to be bound. The calculated binding energies, two-nucleon separation energies, root-mean-square (rms) radii of neutron, proton, matter, and charge distributions, quadrupole deformations, and neutron and proton Fermi surfaces are tabulated and compared with available experimental data. The rms deviation from the 637 mass data is 1.518 MeV, providing one of the best microscopic descriptions for nuclear masses. The drip lines obtained from DRHBc calculations are compared with other calculations, including the spherical relativistic continuum Hartree-Bogoliubov (RCHB) and triaxial relativistic Hartree-Bogoliubov (TRHB) calculations with PC-PK1. The deformation and continuum effects on the limits of the nuclear landscape are discussed. Possible peninsulas consisting of bound nuclei beyond the two-neutron drip line are predicted. The systematics of the two-nucleon separation energies, two-nucleon gaps, rms radii, quadrupole deformations, potential energy curves, neutron densities, neutron mean-field potentials, and pairing energies in the DRHBc calculations are also discussed. In addition, the $α$ decay energies extracted are in good agreement with available data.
Comments:
217 pages, 15 figures, 2 tables, accepted for publication in Atomic Data and Nuclear Data Tables, data file in the TXT form is available for download under "Ancillary files"
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
2201.03216 [pdf]
Atom.Data Nucl.Data Tabl.(2022)·175 citations
09
[Submitted on 10 Jan 2022]
Impact of slow conversions on hybrid stars with sequential QCD phase transitions
Victor P. Goncalves🇧🇷 · Lucas Lazzari🇧🇷
In this paper, we investigate the impact of the phase conversion speed on the properties of hybrid stars with sequential sharp QCD phase transitions. We consider that these hybrid stars possess an inner (outer) core of CFL (2SC) quark matter surrounded by hadronic matter. Assuming that the phase conversions can be slow or rapid, we analyze the dynamical stability of these objects. In particular, we present our predictions for the mass-radius profile and the fundamental eigenfrequencies of hybrid stars with sequential QCD first order phase transitions. Our results demonstrate that the usual stability criteria i.e. $\partial M / \partial P_{0} \geq 0$ , is sufficient only if both conversions are rapid. Moreover, we show that if any of the interfaces has a slow conversion speed, the fundamental eigenfrequencies are significantly modified.
Comments:
7 pages, 4 figures, 1 table. Revised version to be published in EPJC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2201.03304 [pdf]
EPJC(2022)·22 citations
10
[Submitted on 28 Dec 2021]
Steady asymptotic equilibria in conformal relativistic fluids
Esteban Calzetta🇦🇷
When one considers a shock wave in the frame where the shock is at rest, on either side one has a steady flow which converges to equilibrium away from the shock. However, hydrodynamics is unable to describe this flow if the asymptotic velocity is higher than the characteristic speed of the theory. We obtain an exact solution for the decay rate to equilibrium for a conformal fluid in kinetic theory under the relaxation time approximation, and compare it to two hydrodynamic schemes, one accounting for the second moments of the distribution function and thus equivalent, in the small deviations from equilibrium limit, to an Israel-Stewart framework, and another accounting for both second and third moments. While still having a finite characteristic speed, the second model is a significant improvement on the first.
Comments:
Accepted for publication in Phys. Rev. D
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Fluid Dynamics (physics.flu-dyn)
arXiv:
2201.03430 [pdf]
PRD(2022)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE