Nuclear Theory·nucl-th

Tuesday·July 20, 2021

18 papers—8 primary·10 cross-listed

01
Description of the shape of medium and heavy nuclei using a finite deformed one-particle potential with deformation-dependent diffuseness
G. I. Bykhalo · V. N. Orlin · K. A. Stopani
Adjustment of the behavior of the potential energy of nuclear deformation, defined as the sum of the energies of lowest-lying occupied single-particle levels in a deformed finite potential with a pairing correction, is considered by taking into account the dependence of the diffuseness of the surface of the potential on deformation. To verify this approach we construct a non-axial ellipsoidally-deformed potential with a slight (of the order of 1\%) variation of the surface diffuseness at moderate deformations. Parameters of the variation are determined from a calculation for a group of 36 deformed, transitional, and spherical nuclei in the range $50 \leq A \leq 241$ using existing experimental data on static quadrupole moments. In order to test the performed parameter choice, we applied the model to description of the ground-state deformation of the isotopic chains $^{95 - 132}$ Cd and $^{74 - 106}$ Sr. The obtained description of the ground state deformation of the considered nuclei is in agreement with experimental data and results of macro-microscopic models and calculations using the Hartree-Fock-Bogoliubov method.
nucl-th7 citations
02
Microscopic self-consistent description of induced fission: dynamical pairing degree of freedom
Jie Zhao · Tamara Nikšić · Dario Vretenar
The role of dynamical pairing in induced fission dynamics is investigated using the time-dependent generator coordinate method in the Gaussian overlap approximation, based on the microscopic framework of nuclear energy density functionals. A calculation of fragment charge yields for induced fission of $^{228}$ Th is performed in a three-dimensional space of collective coordinates that, in addition to the axial quadrupole and octupole intrinsic deformations of the nuclear density, also includes an isoscalar pairing degree of freedom. It is shown that the inclusion of dynamical pairing has a pronounced effect on the collective inertia, the collective flux through the scission hyper-surface, and the resulting fission yields, reducing the asymmetric peaks and enhancing the contribution of symmetric fission, in better agreement with the empirical trend.
nucl-thnucl-exPRC(2021)·22 citations
03
Hydrodynamic description of the baryon-charged quark-gluon plasma
Lipei Du (Ohio State U.)🇺🇸
One of the primary goals of nuclear physics is studying the phase diagram of Quantum Chromodynamics, where a hypothetical critical point serves as a landmark. A systematic model-data comparison of heavy-ion collisions at center-of-mass energies between 1 and 100 GeV per nucleon is essential for locating the critical point and the phase boundary between the deconfined quark-gluon plasma and the confined hadron resonance gas. At these energies the net baryon density of the system can be high and critical fluctuations can become essential in the presence of the critical point. Simulating their dynamical evolution thus becomes an indispensable part of theoretical modeling. In this thesis we first present the (3+1)-dimensional relativistic hydrodynamic code BEShydro, which solves the equations of motion of second-order Denicol-Niemi-Molnar-Rischke theory, including bulk and shear viscous components as well as baryon diffusion current. We then study the effects caused by the baryon diffusion on the longitudinal dynamics and on the phase diagram trajectories of fluid cells at different space-time rapidities of the system, and how they are affected by critical dynamics near the critical point. We finally explore the evolution of non-hydrodynamic slow processes describing long wavelength critical fluctuations near the critical point, by extending the conventional hydrodynamic description by coupling it to additional explicitly evolving slow modes, and their back-reaction to the bulk matter properties.
nucl-thhep-phnucl-ex5 citations
04
Prospects for study of the effect of the electronic screening on the $α$ decay in the storage rings
F. F. Karpeshin · M. B. Trzhaskovskaya · L. F. Vitushkin
Study of the role of the electron screening in the $α$ decay is advanced, aimed at the experimental test in the storage rings. To this end, systematic calculation of the effect in heavy ions of the nuclei within the Ra to Po domain of the $α$ emitters is conducted within the adiabatic approach. The obtained effect is to slow down the decay by an amount within the percent value. It is of the opposite sign comparing to what is predicted within the conventional frozen shell model. The reason for this divergence is demonstrated. Testing this difference experimentally in storage ring facilities is proposed. It is of great interest for advancing the astrophysical fundamental research.
nucl-thPRC(2022)·3 citations
05
Two-neutrino double-beta decay matrix elements based on relativistic nuclear energy density functional
N. Popara🇭🇷 · A. Ravlić🇭🇷 · N. Paar🇭🇷
Nuclear matrix elements (NMEs) for two-neutrino double-beta decay ( $2 ν β β$ ) are studied in the framework of relativistic nuclear energy density functional (REDF). The properties of nuclei involved in the decay are obtained using the relativistic Hartree-Bardeen-Cooper-Schrieffer theory and relevant nuclear transitions are described using the relativistic proton-neutron quasiparticle random phase approximation based on relativistic energy density functional (REDF-QRPA). Three effective interactions have been employed, including density-dependent meson-exchange (DD-ME2) and point coupling interactions (DD-PC1 and DD-PCX), and pairing correlations are described consistently both in $T = 1$ and $T = 0$ channels using a separable pairing interaction. The optimal values of $T = 0$ pairing strength parameter $V_{0 pp}$ are constrained by the experimental data on $β$ -decay half lives. The $2 ν β β$ matrix elements and half-lives are calculated for several nuclides experimentally known to undergo this kind of decay: $^{48}$ Ca, $^{76}$ Ge, $^{82}$ Se, $^{96}$ Zr, $^{100}$ Mo, $^{116}$ Cd, $^{124}$ Xe, $^{128}$ Te, $^{130}$ Te, $^{136}$ Xe and $^{150}$ Nd. The model dependence of the NMEs and their sensitivity on $V_{0 pp}$ is investigated, and the NMEs obtained using optimal values of $V_{0 pp}$ are discussed in comparison to previous studies. The results of the present work represent an important benchmark for the future applications of the relativistic framework in studies of neutrinoless double-beta decay.
nucl-thnucl-exPRC(2022)·13 citations
06
Highest weight irreducible representations favored by nuclear forces within SU(3)-symmetric fermionic systems
Andriana Martinou · S. Sarantopoulou · K.E. Karakatsanis · Dennis Bonatsos
The consequences of the attractive, short-range nucleon-nucleon (NN) interaction on the wave functions of nuclear models bearing the SU(3) symmetry are reviewed. The NN interaction favors the most symmetric spatial SU(3) irreducible representation (irrep), which corresponds to the maximal spatial overlap among the fermions. The consideration of the highest weight (hw) irreps in nuclei and in alkali metal clusters, leads to the prediction of a prolate to oblate shape transition beyond the mid-shell region. Subsequently, the consequences of the use of the hw irreps on the binding energies and two-neutron separation energies in the rare earth region are discussed within the proxy-SU(3) scheme, by considering a very simple Hamiltonian, containing only the three dimensional (3D) isotropic harmonic oscillator (HO) term and the quadrupole-quadrupole interaction. This Hamiltonian conserves the SU(3) symmetry and treats the nucleus as a rigid rotator.
nucl-thEPJ Web Conf.(2021)·5 citations
07
Properties of Hybrid Stars with Density Dependent Bag Model
Debashree Sen🇮🇳 · Naosad Alam🇮🇳 · Gargi Chaudhuri🇮🇳
The phenomena of deconfinement of hadronic matter into quark matter at high density, relevant to hybrid star (HS) cores, is studied in the present work. The effective chiral model describes the pure hadronic phase while for the quark phase the MIT bag model is chosen with density dependent bag pressure. Phase transition is achieved using Maxwell construction. The effect of variation of the asymptotic value of the bag pressure ( $B_{a s}$ ) is analyzed w.r.t to the mass and radius of the HSs. The presence of hyperons in the hadronic sector also has significant effect on the choice of the value of $B_{a s}$ . Both the hadronic composition and the choice of $B_{a s}$ significantly affect the stability of the star. The gross structural properties of the resultant HS are calculated in static condition and compared with the various constraints on them from different observational and empirical perspectives. The static properties like the maximum gravitational mass of the HS, obtained with $B_{a s}$ =80 MeV fm $^{- 3}$ , is consistent with the limits imposed from the observational analysis of PSR J0348+0432 and PSR J0740+6620. The estimates of $R_{1.4}$ and $R_{1.6}$ of HSs are found to be within the range prescribed from GW170817 analysis. Also the $M - R$ solutions of the HSs are in excellent agreement with the recently obtained NICER data for PSR J0030+0451. The results of maximum surface redshift, obtained with hybrid equation of state, satisfy the constraints from 1E 1207.4-5209 and RX J0720.4-3125. The work is also extended to obtain the tidal deformation properties of the HSs. The obtained value of $Λ_{1.4}$ is consistent with the bound obtained from GW170817 data analysis.
nucl-thJ.Phys.G(2021)·27 citations
08
Connecting the proxy-SU(3) symmetry to the shell model
Dennis Bonatsos · Andriana Martinou · I. E. Assimakis · S.K. Peroulis · S. Sarantopoulou · N. Minkov
Proxy-SU(3) symmetry is an approximation scheme extending the Elliott SU(3) algebra of the sd shell to heavier shells. When introduced in 2017, the approximation had been justified by calculations carried out within the Nilsson model. Recently our group managed to map the cartesian basis of the Elliott SU(3) model onto the spherical shell model basis, proving that the proxy-SU(3) approximation corresponds to the replacement of the intruder orbitals by their de Shalit-Goldhaber partners, paving the way for using the proxy-SU(3) approximation in shell model calculations. The connection between the proxy-SU(3) scheme and the spherical shell model has also been worked out in the original framework of the Nilsson model, with identical results.
nucl-thEPJ Web Conf.(2021)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE