Nuclear Theory·nucl-th

Tuesday·April 4, 2023

16 papers—11 primary·5 cross-listed

01
Investigation of giant dipole resonance in Mo isotopes within TDHF theory
A. Ait Ben Mennana · M.Oulne
The isovector giant dipole resonance (IVGDR) in the chain of even-even Mo isotopes is investigated within the time-dependent Hartree-Fock (TDHF) using the Skyrme force Sly6. The GDR calculated in $^{92 - 108} Mo$ are presented, and compared with the available experimental data. An overall agreement between them is obtained. Moreover, the dipole strength in $^{102 - 108} Mo$ is predicted. Shape phase transition from spherical to oblate as well as shape coexistence (A $\sim$ 100) in Mo isotopes are also investigated in this work. In addition, the correlation between the deformation splitting $Δ E$ and the quadrupole deformation parameter $β_{2}$ is studied. The results confirm that $Δ E$ is proportional to the deformation of nucleus. We also discuss the dependence of GDR strength on some nuclear properties of Skyrme forces, such as the asymmetry energy $a_{s}$ . We find that $a_{s} = 32 M e V$ , corresponding to SLy6, is quite consistent with experimental data.
nucl-thNPA(2023)·2 citations
02
Center-of-mass momentum dependence of short-range correlations with the coarse-grained Granada potential
P.R. Casale · J.E. Amaro · E. Ruiz Arriola · I. Ruiz Simo
The effect of the center of mass motion on the high-momentum distributions of correlated nucleon pairs is studied by solving the Bethe-Goldstone equation in nuclear matter with the Granada nucleon-nucleon potential. We show that this coarse-grained potential reduces the problem to an algebraic linear system of five (ten) equations for uncoupled (coupled) partial waves that can be easily solved. The corresponding relative wave functions of correlated pn, pp and nn pairs are computed for different values of their CM momentum. We find that the pn pairs dominate the high-momentum tail of the relative momentum distribution, and that this only depends marginally on center of mass momentum. Our results provide further justification and agreement for the factorization approximation commonly used in the literature. This approximation assumes that the momentum distribution of nucleon pairs can be factorized as the product of the center of mass momentum distribution and the relative momentum distribution.
nucl-thPRC(2023)·9 citations
03
On statistical fluctuations in collective flows
Wei-Liang Qian🇨🇳 · Kai Lin🇨🇳 · Chong Ye🇨🇳 · Jin Li🇨🇳 · Yu Pan🇨🇳 · Rui-Hong Yue🇨🇳
In relativistic heavy-ion collisions, event-by-event fluctuations are known to have non-trivial implications. Even though the probability distribution is geometrically isotropic for the initial conditions, the anisotropic $ε_{n}$ still differs from zero owing to the statistical fluctuations in the energy profile. On the other hand, the flow harmonics extracted from the hadron spectrum using the multi-particle correlators are inevitably subjected to non-vanishing variance due to the finite number of hadrons emitted in individual events. As one aims to extract information on the fluctuations in the initial conditions via flow harmonics and their fluctuations, finite multiplicity may play a role in interfering with such an effort. In this study, we explore the properties and impacts of such fluctuations in the initial and final states, which both notably appear to be statistical ones originating from the finite number of quanta of the underlying system. We elaborate on the properties of the initial-state eccentricities for the smooth and event-by-event fluctuating initial conditions and their distinct impacts on the resulting flow harmonics. Numerical simulations are performed. The possible implications of the present study are also addressed.
nucl-thUniverse(2023)·5 citations
04
Electric and magnetic conductivities in magnetized fermion systems
Hao-Hao Peng🇨🇳 · Xin-Li Sheng🇮🇹 · Shi Pu🇨🇳 · Qun Wang🇨🇳
In Wigner function approach with relaxation time approximation, we calculate electric and magnetic conductivities of a fermion system in the strong magnetic field. The linear response has been calculated to the perturbation of electromagnetic fields on the background constant magnetic field. The Wigner function is separated into an equilibrium part in the background magnetic field and an off-equilibrium part induced by perturbative fields. The analytical expression for the equilibrium part and the corresponding equilibrium conditions are given. For the off-equilibrium part, we obtain the kinetic equation at the leading order in $ℏ$ from the master equation of the Wigner function. When perturbative fields only depend on the proper time, the off-equilibrium part can be analytically solved from which the vector and axial vector currents are obtained. We obtain the longitudinal and transverse Ohm conductivities as well as Hall conductivity as the linear response of the vector current to the perturbative electric field. The behaviors of these conductivities as functions of the evolving time, relaxation time, particle mass, and strength of the background magnetic field are investigated both analytically and numerically.
nucl-thhep-thPRD(2023)·7 citations
05
Polaronic Proton and Diproton Clustering in Neutron-Rich Matter
Hiroyuki Tajima · Hajime Moriya · Wataru Horiuchi · Eiji Nakano · Kei Iida
We show that strong spin-triplet neutron-proton interaction causes polaronic protons to occur in neutron matter at subnuclear densities and nonzero temperature. As the neutron density increases, proton spectra exhibit a smooth crossover from a bare impurity to a repulsive polaron branch; this branch coexists with an attractive polaron branch. With the neutron density increased further, the attractive polarons become stable with respect to deuteron formation. For two adjacent protons, we find that the polaron effects and the neutron-mediated attraction are sufficient to induce a bound diproton, which leads possibly to diproton formation in the surface region of neutron-rich nuclei in laboratories as well as in neutron stars.
nucl-thastro-ph.HEcond-mat.quant-gascond-mat.supr-con+1PLB(2024)·10 citations
06
Gamow Shell Model description of $^{7}$ Li and elastic scattering reaction $^{4}$ He( $^{3}$ H, $^{3}$ H) $^{4}$ He
J.P. Linares Fernández🇫🇷 · M. Płoszajczak🇫🇷 · N. Michel🇨🇳
Spectrum of $^{7}$ Li and elastic scattering reaction $^{4}$ He( $^{3}$ H, $^{3}$ H) $^{4}$ He are studied using the unified description of the Gamow shell model in the coupled-channel formulation (GSMCC). The reaction channels are constructed using the cluster expansion with the two mass partitions [ $^{4}$ He + $^{3}$ H], [ $^{6}$ Li + n].
nucl-thActa Phys.Polon.Supp.(2023)·0 citations
07
Semiclassical origin of nuclear ground-state octupole deformations
Ken-ichiro Arita
Background: Ground-state octupole deformations are suggested in nuclei located in the north-east neighbor of the doubly magic nuclei on the nuclear chart (N,Z), such as those in Ba and Ra-Th regions. This systematics has been attributed to the parity mixing of the approximately degenerate Delta l=3 pair of single-particle levels near the Fermi surface. Purpose: Nuclear deformations are governed in most cases by the gross shell structures of the single-particle spectra. I will consider the systematics in octupole deformation from the view point of the gross shell structure, and investigate the mechanism of its manifestation using the semiclassical periodic-orbit theory (POT), which describes the quantum shell effect by means of the periodic orbits (POs) in the corresponding classical system. Methods: To focus on the role of deformation, simplified infinite-well (cavity) and radial power-law potential models are employed taking account of quadrupole and octupole shape degrees of freedom. Nuclear ground-state deformations are investigated over the nuclear chart, and the properties of the deformed shell structures are analyzed by means of the semiclassical POT. Results and conclusions: The systematics in nuclear ground-state octupole deformations are reproduced in simplified mean-field potential models either with or without parity mixing between Delta l=3 pair of levels. The strong octupole deformed shell effect at above the spherical shell closures are explained simply and clearly using the semiclassical POT. They are associated with the local restoration of dynamical symmetry, which enhance the contribution of classical POs to the gross shell effect.
nucl-thPRC(2023)·2 citations
08
Allowed $β^{-}$ decay of bare atoms with A $\sim$ 60-80 in stellar environments
Arkabrata Gupta · Chirashree Lahiri · S. Sarkar
We have calculated $β^{-}$ decay rates to the continuum and bound states of some fully ionized atoms in the stellar s-process environment having free electron density and temperature in the range $n_{e} = 1 0^{26}$ cm $^{- 3} - 1 0^{27}$ cm $^{- 3}$ and $T = 1 0^{8}$ K - $5 \times 1 0^{8}$ K, respectively. The presence of bare atoms in these particular situations has been confirmed by solving Saha ionization equation taking into account the ionization potential depression (IPD). At these temperatures, low lying excited energy levels of parent nuclei may have thermal equilibrium population and those excited levels may also decay via $β^{-}$ emission. The Nuclear Matrix Element (NME) of all the transitions of the set of 15 nuclei is calculated using nuclear shell-model. These NME are then used to calculate the comparative half-life ( $f t_{1/2}$ ) of the transitions. Calculated terrestrial half-lives of the $β^{-}$ decays are in good agreement with the experimental results in most of the cases. Decay to bound and continuum states of bare atoms from ground/isomeric levels and excited nuclear levels have been calculated separately. The ratio of bound state to continuum state decay rates as a function of IPD modified $Q$ -value reveals that bound state $β^{-}$ decay rate may compete and even dominate for $Q$ -value $<$ 100 keV. The importance of the bound state $β^{-}$ decay in stellar situations has been shown explicitly. We have calculated total $β^{-}$ decay rates (bound state plus continuum state) taking into account IPD corrected neutral atom $Q$ -value as a function of density and temperature. We have also presented results for the stellar $β^{-}$ half-lives and compared the ratio of neutral atom to bare atom half-lives for different density and temperature combinations. These results may be useful for s-process nucleosynthesis calculations.
nucl-thPRC(2023)·3 citations
09
Relativistic second-order spin hydrodynamics: an entropy-current analysis
Rajesh Biswas🇵🇱 · Asaad Daher🇵🇱 · Arpan Das🇵🇱 · Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱
We present a new derivation of Israel-Stewart-like relativistic second-order dissipative spin hydrodynamic equations using the entropy current approach. In our analysis, we consider a general energy-momentum tensor with symmetric and anti-symmetric parts. Moreover, the spin tensor, which is not separately conserved, has a simple phenomenological form that is antisymmetric only in the last two indices. Apart from the evolution equations for energy density, fluid flow, and spin density, we also find relaxation-type dynamical equations for various dissipative currents. The latter are consistently derived within the second-order theory as gradient corrections to the energy-momentum and spin tensors. We argue that this approach correctly reproduces the corresponding Navier-Stokes limit of spin hydrodynamic equations. Throughout our analysis, the spin chemical potential is considered a $O (\partial)$ quantity in the hydrodynamic gradient expansion and reduces to thermal vorticity in the global equilibrium. New coefficients appearing in the generalized spin hydrodynamic equations are undetermined and can only be evaluated within a proper underlying microscopic theory of a given system.
nucl-thhep-phPRD(2023)·70 citations
10
Constraints on the in-medium nuclear interaction from chiral symmetry and Lattice-QCD
G. Chanfray🇫🇷 · H. Hansen🇫🇷 · J. Margueron🇫🇷
In this paper we discuss the combined effects on nuclear matter properties of the quark confinement mechanism in nucleon and of the chiral effective potential resulting from the spontaneous breaking of the chiral symmetry in nuclear matter. Based on the Nambu-Jona-Lasinio predictions, it is shown that the chiral potential acquires a specific scalar field cubic dependence, which contributes to the three-body interaction. We also discuss the constraints induced by Lattice-QCD on the model parameters governing the saturation properties. We introduce the term "QCD-connected parameters" for these quantities. We demonstrate that chiral symmetry and Lattice-QCD provide coherent constraints on the in-medium nuclear interaction, suggesting a fundamental origin of the saturation mechanism.
nucl-thhep-latEPJA(2023)·8 citations
11
Two-body double pole and three-body bound states: physical and unphysical quark masses
V. S. Timoteo🇧🇷 · U. van Kolck🇫🇷
We solve the Faddeev bound-state equations for three particles with simple two-body nonlocal, separable potentials that yield a scattering length twice as large as a positive effective range, as indicated by some lattice QCD simulations. Neglecting shape parameters, the two-body bound state is a double pole. For bosons we obtain a correlation between three- and two-body energies. For nucleons, this correlation depends additionally on the ratio of effective ranges in the two two-body $S$ -wave channels. When this ratio takes the value suggested by lattice QCD, our three-body energy agrees well with a direct lattice determination. When this ratio takes the experimental value, we find a three-body bound state with energy close to that of the physical triton. We suggest that results could be improved systematically with distorted-wave perturbation theory around a separable potential whose form factor is an inverse square root of momentum squared.
nucl-thPLB(2024)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE