Nuclear Theory·nucl-th

Tuesday·April 23, 2024

10 papers—6 primary·4 cross-listed

01
The axially-deformed relativistic quasiparticle random phase approximation based on point-coupling interactions
A. Ravlić🇺🇸 · T. Nikšić🇭🇷 · Y. F. Niu🇨🇳 · P. Ring🇩🇪 · N. Paar🇭🇷
Collective nuclear excitations, like giant resonances, are sensitive to nuclear deformation, as evidenced by alterations in their excitation energies and transition strength distributions. A common theoretical framework to study these collective modes, the random-phase approximation (RPA), has to deal with large dimensions spanned by all possible particle-hole configurations satisfying certain symmetries. This work aims to establish a new theoretical framework to study the impact of deformation on spin-isospin excitations, that can provide fast and reliable solutions of the RPA equations. The nuclear ground state is determined with the axially-deformed relativistic Hartree-Bogoliubov (RHB) model based on relativistic point-coupling energy density functionals (EDFs). To study the excitations in the charge-exchange channel, an axially-deformed proton-neutron relativistic quasiparticle RPA (pnRQRPA) is developed in the linear response approach. After benchmarking the axially-deformed pnRQRPA in the spherical limit, a study of spin-isospin excitations including Fermi, Gamow-Teller (GT), and Spin-Dipole (SD) is performed for selected $p f$ -shell nuclei. For GT transitions, it is demonstrated that deformation leads to considerable fragmentation of the strength function. A mechanism inducing the fragmentation is studied by decomposing the total strength to different projections of total angular momentum $K$ and constraining the nuclear shape to either spherical, prolate or oblate. A similar fragmentation is also observed for SD transitions, although somewhat moderated by the complex structure of these transitions, while the Fermi strength is almost shape-independent. The axially-deformed pnRQRPA introduced in this work opens perspectives for future studies of deformation effects on astrophysically relevant weak interaction processes, in particular beta decay and electron capture.
nucl-thnucl-exPRC(2024)·9 citations
02
Light and hyper nuclei formation at $s_{NN} =$ 3 GeV Au+Au collisions using Wigner coalescence approach
L. K. Liu🇨🇳 · C. L. Hu🇨🇳 · X. H. He🇨🇳 · S. S. Shi🇨🇳 · G. N. Xie🇨🇳
The production of light nuclei and hyper-nuclei in heavy-ion collisions, particularly at high baryon density, is crucial for understanding the dynamical evolution of the collision system and exploring the internal state of nuclear matter of compacted stellar object. Despite being a topic of ongoing debate, an improved theoretical understanding is necessary. In this work, production of light nuclei ( $d$ , $t$ , $^{3}$ He, $^{4}$ He) and hyper-nuclei ( $_{Λ}^{3}$ H, $_{Λ}^{4}$ H) was investigated using the JAM microscopic transport model combined with an afterburner coalescence process at $s_{NN} =$ 3 GeV Au+Au collisions. The formation of a specific nucleus during the coalescence process is determined by its Wigner function. The comparison of the calculations for $p_{T}$ spectra, average $p_{T}$ , and rapidity distributions to the measurements from the STAR experiment was performed. We investigated the dynamic information carried by light nuclei and determined the averaged spatial distance $⟨ Δ R ⟩$ and momentum difference $⟨ Δ P ⟩$ of constituent nucleons ( $Λ$ ) for each nucleus species.
nucl-thPLB(2024)·7 citations
03
Radial and orbital decomposition of charge radii of Ca nuclei:Comparative study of Skyrme and Fayans functionals
T. Inakura · N. Hinohara · H. Nakada
We investigate the charge and point-proton radii of the Ca nuclei in detail in the density functional theory framework. As the Fayans energy density functional provides characteristic $N$ -dependence, successfully describing the parabolic behavior of the differential charge radii in $20 \leq N \leq 28$ , we pose our particular focus on its physics origin, by decomposing them into the radial and orbital contributions. The results are compared with those from the Skyrme plus usual pairing functional, which is taken as a representative of the functionals having normal pairing channels. We point out that, because the enhancement of the differential charge radii in $N < 20$ with the Fayans functional, which is contradictory with the data, has the origin parallel to the parabolic behavior in $20 \leq N \leq 28$ , it is significant to describe both $N$ regions simultaneously.
nucl-thPRC(2024)·5 citations
04
Fission barriers with Weizsäcker-Skyrme mass model
Ning Wang · Liu Min
Based on Weizsäcker-Skyrme (WS4) mass model, the fission barriers of nuclei are systematically studied. Considering the shell corrections, the macroscopic deformation energy and a phenomenological residual correction, the fission barrier heights for nuclei with $Z ⩾ 82$ can be well described, with an rms deviation of 0.481 MeV with respect to 71 empirical barrier heights. In addition to the shell correction at the ground state, the shell correction at the saddle point and its relative value are also important for both deformed nuclei and spherical nuclei. The fission barriers for nuclei far from the $β$ -stability line and super-heavy nuclei are also predicted with the proposed approach.
nucl-thCPC(2024)·5 citations
05
Ab initio description of monopole resonances in light- and medium-mass nuclei: III. Moments evaluation in ab initio PGCM calculations
Andrea Porro🇩🇪 · Thomas Duguet🇫🇷 · Jean-Paul Ebran🇫🇷 · Mikael Frosini🇫🇷 · Robert Roth🇩🇪 · Vittorio Somà🇫🇷
The paper is the third of a series dedicated to the ab initio description of monopole giant resonances in mid-mass closed- and open-shell nuclei via the so-called projected generator coordinate method. The present focus is on the computation of the moments $m_{k}$ of the monopole strength distribution, which are used to quantify its centroid energy and dispersion. First, the capacity to compute low-order moments via two different methods is developed and benchmarked for the $m_{1}$ moment. Second, the impact of the angular momentum projection on the centroid energy and dispersion of the monopole strength is analysed before comparing the results to those obtained from consistent quasi-particle random phase approximation calculations. Next, the so-called energy weighted sum rule (EWSR) is investigated. First, the appropriate ESWR in the center-of-mass frame is derived analytically. Second, the exhaustion of the intrinsic EWSR is tested in order to quantify the (unwanted) local-gauge symmetry breaking of the presently employed chiral effective field theory ( $χ$ EFT) interactions. Finally, the infinite nuclear matter incompressibility associated with the employed $χ$ EFT interactions is extracted by extrapolating the finite-nucleus incompressibility computed from the monopole centroid energy.
nucl-thEPJA(2024)·13 citations
06
$Λ$ polarization in very high energy heavy ion collisions as a probe of the Quark-Gluon Plasma formation and properties
Andrea Palermo🇺🇸 · Eduardo Grossi🇮🇹 · Iurii Karpenko🇨🇿 · Francesco Becattini🇮🇹
We have studied the spin polarization of $Λ$ hyperons in heavy ion collisions at center-of-mass energies $s_{N N} = 200$ GeV and $s_{N N} = 5.02$ TeV carried out at RHIC and LHC colliders. We have calculated the mean spin vector at local thermodynamic equilibrium, including all known first-order terms in the gradients of the thermo-hydrodynamic fields, assuming that the hadronization hypersurface has a uniform temperature. We have also included the feed-down contributions to the polarization of $Λ$ stemming from the decays of polarized $Σ^{*}$ and $Σ^{0}$ hyperons. The obtained results are in good agreement with the data. In general, the component of the spin vector along the global angular momentum, orthogonal to the reaction plane, shows strong sensitivity to the initial longitudinal flow velocity. Furthermore, the longitudinal component of the spin vector turns out to be very sensitive to the bulk viscosity of the plasma at the highest LHC energy. Therefore, the azimuthal dependence of spin polarization can effectively constrain the initial hydrodynamic conditions and the transport coefficients of the Quark Gluon Plasma.
nucl-thhep-phhep-thEPJC(2024)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE

The axially-deformed relativistic quasiparticle random phase approximation based on point-coupling interactions

Light and hyper nuclei formation at sNN​​= 3 GeV Au+Au collisions using Wigner coalescence approach

Radial and orbital decomposition of charge radii of Ca nuclei:Comparative study of Skyrme and Fayans functionals

Fission barriers with Weizsäcker-Skyrme mass model

Ab initio description of monopole resonances in light- and medium-mass nuclei: III. Moments evaluation in ab initio PGCM calculations

Λ polarization in very high energy heavy ion collisions as a probe of the Quark-Gluon Plasma formation and properties

Affiliations

Light and hyper nuclei formation at $s_{NN} =$ 3 GeV Au+Au collisions using Wigner coalescence approach

$Λ$ polarization in very high energy heavy ion collisions as a probe of the Quark-Gluon Plasma formation and properties