Nuclear Theory·nucl-th

Thursday·October 12, 2017

13 papers—11 primary·2 cross-listed

01
[Submitted on 10 Oct 2017]
Electromagnetic transitions in the algebraic cluster model
R. Bijker · O.A. Díaz-Caballero
We study electromagnetic transition rates in the framework of the algebraic cluster model. The concept of shape-phase transitions is used to propose a mechanism that allows to have interband and intraband quadrupole transitions of comparable strength, as observed in 12C.
Comments:
6 pages, 2 tables, 4 figures, Physica Scripta Special Issue: Shapes and Symmetries, in press
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.03767 [pdf]
Phys.Scripta(2017)·3 citations
02
[Submitted on 11 Oct 2017]
Octupole deformation in the ground states of even-even $Z \sim 96, N \sim 196$ actinides and superheavy nuclei
S. E. Agbemava · A. V. Afanasjev
A systematic search for axial octupole deformation in the actinides and superheavy nuclei with proton numbers $Z = 88 - 126$ and neutron numbers from two-proton drip line up to $N = 210$ has been performed in covariant density functional theory (DFT) using four state-of-the-art covariant energy density functionals representing different model classes. The nuclei in the $Z \sim 96, N \sim 196$ region of octupole deformation have been investigated in detail and the systematic uncertainties in the description of their observables have been quantified. Similar region of octupole deformation exists also in Skyrme DFT and microscopic+macroscopic approach but it is centered at somewhat different particle numbers. Theoretical uncertainties in the predictions of the regions of octupole deformation are increasing on going to superheavy nuclei with $Z \sim 120, N \sim 190$ . There are no octupole deformed nuclei for $Z = 112 - 126$ in covariant DFT calculations. This agrees with Skyrme DFT calculations, but disagrees with Gogny DFT and microscopic+macroscopic calculations which predict extended $Z \sim 120, N \sim 190$ region of octupole deformation.
Comments:
arXiv admin note: text overlap with arXiv:1603.03414
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.03867 [pdf]
PRC(2017)·49 citations
03
[Submitted on 11 Oct 2017]
Recent progress in the studies of neutron rich and high- $Z$ systems within the covariant density functional theory
A. V. Afanasjev · S. E. Agbemava · D. Ray · P. Ring
The analysis of statistical and systematic uncertainties and their propogation to nuclear extremes has been performed. Two extremes of nuclear landscape (neutron-rich nuclei and superheavy nuclei) have been investigated. For the first extreme, we focus on the ground state properties. For the second extreme, we pay a particular attention to theoretical uncertainties in the description of fission barriers of superheavy nuclei and their evolution on going to neutron-rich nuclei.
Comments:
11 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.03869 [pdf]
Acta Physica Polonica B Proceedings Suppl…·0 citations
04
[Submitted on 11 Oct 2017]
Effects of finite coverage on global polarization observables in heavy ion collisions
Shaowei Lan🇨🇳 · Zi-Wei Lin🇨🇳 · Shusu Shi🇨🇳 · Xu Sun🇨🇳
In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented polarization signals for $Λ$ hyperons and possible spin alignment signals for $ϕ$ mesons. Here we discuss the effects of finite coverage on these observables. The results from a multi-phase transport and a toy model both indicate that a pseudorapidity coverage narrower than $∣ η ∣ <\sim 1$ will generate a larger value for the extracted $ϕ$ -meson $ρ_{00}$ parameter; thus a finite coverage can lead to an artificial deviation of $ρ_{00}$ from 1/3. We also show that a finite $η$ and $p_{T}$ coverage affect the extracted $p_{H}$ parameter for $Λ$ hyperons when the real $p_{H}$ value is non-zero. Therefore proper corrections are necessary to reliably quantify the global polarization with experimental observables.
Comments:
Accepted by PLB, major revision on simulation results of Lambda global polarization parameter
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.03895 [pdf]
PLB(2018)·18 citations
05
[Submitted on 11 Oct 2017]
Shape transitions in odd-mass $γ$ -soft nuclei within the interacting boson-fermion model based on the Gogny energy density functional
K. Nomura · R Rodríguez-Guzmán · L. M. Robledo
The interacting boson-fermion model (IBFM), with parameters determined from the microscopic Hartree-Fock-Bogoliubov (HFB) approximation, based on the parametrization D1M of the Gogny energy density functional (EDF), is employed to study the structural evolution in odd-mass $γ$ -soft nuclei. The deformation energy surfaces of even-even nuclei, single-particle energies and occupation probabilities of the corresponding odd-mass systems have been obtained within the constrained HFB approach. Those building blocks are then used as a microscopic input to build the IBFM Hamiltonian. The coupling constants of the boson-fermion interaction terms are taken as free parameters, fitted to reproduce experimental low-lying spectra. The diagonalization of the IBFM Hamiltonian provides the spectroscopic properties for the studied odd-mass nuclei. The procedure has been applied to compute low-energy excitation spectra and electromagnetic transition rates, in the case of the $γ$ -soft odd-mass systems $^{129 - 137}$ Ba, $^{127 - 135}$ Xe, $^{129 - 137}$ La and $^{127 - 135}$ Cs. The calculations provide a reasonable agreement with the available experimental data and agree well with previous results based on the relativistic mean-field approximation.
Comments:
14 pages, 20 figures, 8 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.03908 [pdf]
PRC(2017)·32 citations
06
[Submitted on 11 Oct 2017]
Translation invariance and antisymmetry in the theory of the nucleon optical model
R.C.Johnson
The first step in any formalism that aims to connect a many-nucleon theory of nucleon-nucleus scattering and the concept of an optical model potential in the sense pioneered by Feshbach is to explain what is meant by the optical model wavefunction. By definition this is a function of a single space coordinate plus a set of single nucleon internal variables. This article gives a critique of the definitio as it is frequently expressed in 2nd Quantisation language and suggest a new definition which is more consistent with the requirements of antisymmetry and translational invariance. A modification of the time-dependent Green's function formalism is suggested.
Comments:
9 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.03994 [pdf]
PRC(2017)·10 citations
07
[Submitted on 11 Oct 2017]
Role of isospin and its conservation in neutron-rich fission fragments
Swati Garg · Bhoomika Maheshwari · Ashok Kumar Jain
Following upon our earlier paper [1] containing some initial results, we present detailed discussion and complete results in this paper, which provide the first direct evidence for the validity of isospin as a nearly good quantum number in neutron-rich systems. The evidence comes from the reproduction of the general features of the partition-wise relative yields of neutron-rich fission fragments produced in two heavy-ion induced fusion fission reactions, namely $^{208}$ Pb ( $^{18}$ O, f) and $^{238}$ U ( $^{18}$ O, f), by using the concept of isospin conservation. To fix the isospin values and use the isospin algebra, we invoke what we term as Kelson's conjectures. We present a consistent scheme for isospin assignments based on these considerations. Our calculated results confirm that isospin behaves as an approximately good quantum number in neutron-rich systems, in this case, the fission fragments.
Comments:
25 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.04051 [pdf]
Phys.Scripta(2018)·7 citations
08
[Submitted on 11 Oct 2017]
Collective Neutrino Oscillations and Nucleosynthesis
A.B. Balantekin (Wisconsin U., Madison)🇺🇸
The emergent phenomenon of collective neutrino oscillations arises from neutrino-neutrino interactions in environments with very large number of neutrinos. Since such environments are likely sites of the heavy-element synthesis, understanding all aspects of collective neutrino oscillations seems to be necessary for a complete accounting of nucleosynthesis. I briefly summarize some of the salient features along with recent work on the properties and astrophysical applications of the collective neutrino oscillations.
Comments:
6 pages, 1 figure, Proceedings of the OMEG17 Conference
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1710.04108 [pdf]
AIP Conf.Proc.(2018)·9 citations
09
[Submitted on 11 Oct 2017]
The evolving many-nucleon theory of nuclear rotations
David J. Rowe
The many approaches that have been pursued in seeking an understanding of nuclear rotational dynamics are reviewed and reassessed with a view to their development in the light of recent progress and the research tools that are now available. A motivation for this review is the widespread observation of nuclear shape coexistence and sequences of rotational states in all regions of the nuclear periodic table combined with the recognition that the study of the rotational dynamics of quantum fluids has led to significant advances in the quantum theory of many-boson systems. Recent experimental investigations of the rotational dynamics of a low-temperature $^{6}$ Li gas indicate that its slow rotational flows are likewise the irrotational flows of a superfluid. In this context, the dynamics of rotating nuclei are of fundamental interest because the nucleus is a unique zero-temperature finite many-fermion quantum system. A promising approach is provided by algebraic mean-field theory which, as its name suggests, is a combination of algebraic and mean-field methods. Static mean-field theories play a central role in many-body theory by defining optimal independent-particle and independent quasi-particle basis states for the quantum mechanics of many-fermion systems. Their time-dependent extensions also lead, in the small-amplitude random-phase approximation, to the quantisation of the classical normal-mode vibrations of many-fermion systems about their static equilibrium states. This review shows that mean-field methods become significantly more powerful when combined with algebraic methods and an appropriate coupling scheme for the nuclear shell model.
Comments:
45 pages , 4 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.04150 [pdf]
1 citation
10
[Submitted on 11 Oct 2017]
Estimation of surface tension in nuclei
N.G.Goncharova
Coefficients of surface tension for even-even nuclei were estimated using its dependence of nuclear rigidity. The values of nuclear rigidity were obtained owing to its connection to mean squared deformations. The correlation of estimated surface tension coefficients with data on nuclear shapes was revealed.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.04174 [pdf]
Phys.Part.Nucl.(2019)·2 citations
11
[Submitted on 11 Oct 2017]
Wilsonian renormalization group and the Lippmann-Schwinger equation with a multitude of cutoff parameters
E. Epelbaum · J. Gegelia · Ulf-G. Meißner
The Wilsonian renormalization group approach to the Lippmann-Schwinger equation with a multitude of cutoff parameters is introduced. A system of integro-differential equations for the cutoff-dependent potential is obtained. As an illustration, a perturbative solution of these equations with two cutoff parameters for a simple case of an S-wave low-energy potential in the form of a Taylor series in momenta is obtained. The relevance of the obtained results for the effective field theory approach to nucleon-nucleon scattering is discussed.
Comments:
6 pages, no figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1710.04178 [pdf]
Commun.Theor.Phys.(2018)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE