Nuclear Theory·nucl-th

Tuesday·September 19, 2023

21 papers—13 primary·8 cross-listed

01
Probing hadron-quark phase transition in twin stars using $f$ -modes
Bikram Keshari Pradhan🇮🇳 · Debarati Chatterjee🇮🇳 · David Edwin Alvarez-Castillo🇵🇱
Although it is conjectured that a phase transition from hadronic to deconfined quark matter in the ultrahigh-density environment of Neutron Stars (NS), the nature of phase transition remains an unresolved mystery. Furthermore, recent efforts reveal that the finite surface tension effects can lead to a mixed phase with different geometric shapes (so-called "pasta" phases), leading to a smooth phase transition from hadronic to quark matter in the NS interior. Depending on whether there is a strong or a pasta-induced smooth first-order phase transition, one may expect a third family of stable, compact stars or "twin stars" to appear, with the same mass but different radii compared to NSs. The possibility of identifying twin stars using astrophysical observations has been a subject of interest. This study investigates the potential of probing the nature of the hadron-quark phase transition through future gravitational wave (GW) detections from fundamental ( $f$ -) mode oscillations in Neutron Stars. Using a newly developed model that parametrizes the hadron-quark phase transition with ``pasta phases," we calculate $f$ -mode characteristics within a full general relativistic framework. We then use Universal Relations in GW asteroseismology to derive stellar properties from the detected mode parameters. Our findings suggest that detecting GWs from $f$ -modes with third-generation GW detectors offers a promising scenario for the existence of twin stars. However, we also estimate various uncertainties in determining the mode parameters and conclude that these uncertainties make it more challenging to identify the nature of the hadron-quark phase transition.
nucl-thastro-ph.HEgr-qcMNRAS(2024)·23 citations
02
Global trends of the electric dipole polarizability from shell-model calculations
José Nicolás Orce · Cebo Ngwetsheni · B. Alex Brown
Shell-model calculations of the electric dipole (E1) polarizability have been performed for the ground state of selected p- and sd-shell nuclei, substantially advancing previous knowledge. Our results are slightly larger compared with the somewhat more scattered photo-absorption cross-section data, albeit agreeing with ab initio calculations at shell closures and presenting a smooth trend that follows the leptodermus approximation provided by the finite-range droplet model (FRDM). The total E1 strengths also show an increasing trend proportional to the mass number which follows from the classical oscillator strength (TRK) sum rule for the E1 operator. The enhancement of the energy-weighted sum over E1 excitations with respect to the TRK sum rule arises from the use of experimental single-particle energies and the residual particle-hole interaction.
nucl-thnucl-exPRC(2023)·13 citations
03
Azimuthal distribution of exponential format for particle collective motions in heavy-ion collisions under asynchronous assumption
Yicheng Feng🇺🇸
Particle azimuth distributions are widely studied in heavy-ion collisions. They are often expanded in Fourier series to extract anisotropic flow harmonics simultaneously. It was recently proposed that the different orders of flows could happen asynchronously or noninterdependently. This study extends this idea to an exponential format of the azimuth distribution, which makes it straightforward to extract the asynchronous flow coefficients. We compare these new coefficients to the conventional ones, and find consistency in the leading coefficient and discrepancy in higher-order ones.
nucl-thnucl-ex0 citations
04
Medium modification of pion production in low energy Au+Au collisions
Christian Kummer🇩🇪 · Kai Gallmeister🇩🇪 · Lorenz von Smekal🇩🇪
There is a major mismatch between the charged pion yields in Au+Au collisions at low energies calculated by various transport models and the experimental measured values from the Hades collaboration. In this work, reasonable improvements on the equation of state, in-medium modification of cross sections, and the influence of the nuclear potential for Delta resonances will be investigated in the framework of the GiBUU transport model. As a result, we demonstrate that theoretical calculations can indeed describe the charged pion yields measured by Hades for Au+Au collisions rather well, but that a mismatch then remains between calculations and data for the yields of neutral pions extracted from dileptons within the same experiment.
nucl-thhep-phPRC(2024)·6 citations
05
Conservation and breaking of pseudospin symmetry
T.-T. Sun · Z. P. Li · P. Ring
Pseudospin symmetry (PSS) is a relativistic dynamical symmetry connected with the lower component of the Dirac spinor. Here, we investigate the conservation and breaking of PSS in the single-nucleon resonant states, as an example, using Green's function method that provides a novel way to precisely describe not only the resonant energies and widths but also the spacial density distributions for both narrow and wide resonances. The PSS restoration and breaking are perfectly displayed in the evolution of resonant parameters and density distributions with the potential depth: In the PSS limit, i.e., when the attractive scalar and repulsive vector potentials have the same magnitude but opposite sign, PSS is exactly conserved with strictly the same energy and width between the PS partners as well as identical density distributions of the lower components. As the potential depth increases, the PSS is broken gradually with energy and width splittings and a phase shift in the density distributions.
nucl-thPLB(2023)·9 citations
06
Persistent vibrational structure in $^{110 - 116}$ Cd
N. Gavrielov🇺🇸 · J.E. Garcia-Ramos🇪🇸 · P. Van Isacker🇫🇷 · A. Leviatan🇮🇱
The empirical spectra and $E 2$ decay rates in $^{110, 112, 114, 116}$ Cd are shown to be consistent with a vibrational interpretation for low-lying normal states, coexisting with a single deformed $γ$ -soft band of intruder states. The observed deviations from this paradigm show up in particular non-yrast states, which are properly described by a Hamiltonian with U(5) partial dynamical symmetry. The latter is characterized by a good (broken) symmetry in most (in selected) normal states, weakly coupled to intruder states.
nucl-thPRC(2023)·12 citations
07
Global properties of nuclei at finite-temperature within the covariant energy density functional theory
Ante Ravlić · Esra Yüksel · Tamara Nikšić · Nils Paar
In stellar environments nuclei appear at finite temperatures, becoming extremely hot in core-collapse supernovae and neutron star mergers. However, due to theoretical and computational complexity, most model calculations of nuclear properties are performed at zero temperature, while those existing at finite temperatures are limited only to selected regions of the nuclide chart. In this study we perform the global calculation of nuclear properties for even-even $8 \leq Z \leq 104$ nuclei at temperatures in range $0 \leq T \leq 2$ MeV. Calculations are based on the finite temperature relativistic Hartree-Bogoliubov model supplemented by the Bonche-Levit-Vautherin vapor subtraction procedure. We find that near the neutron-drip line the continuum states have significant contribution already at moderate temperature $T \approx 1$ MeV, thus emphasising the necessity of the vapor subtraction procedure. Results include neutron emission lifetimes, quadrupole deformations, neutron skin thickness, proton and neutron pairing gaps, entropy and excitation energy. Up to the temperature $T \approx 1$ MeV nuclear landscape is influenced only moderately by the finite-temperature effects, mainly by reducing the pairing correlations. As the temperature increases further, the effects on nuclear structures become pronounced, reducing both the deformations and the shell effects.
nucl-thPRC(2024)·9 citations
08
Fission Fragment Mass and Kinetic Energy Yields of Fermium Isotopes
K. Pomorski🇵🇱 · A. Dobrowolski🇵🇱 · B. Nerlo-Pomorska🇵🇱 · M. Warda🇵🇱 · A. Zdeb🇵🇱 · J. Bartel🇫🇷 · H. Molique🇫🇷 · C. Schmitt🇫🇷 · Z. G. Xiao🇨🇳 · Y. J. Chen🇨🇳 · L. L. Liu🇨🇳
A rapidly converging 4-dimensional Fourier shape parametrization is used to model the fission process of heavy nuclei. Potential energy landscapes are computed within the macroscopic-microscopic approach, on top of which the multi-dimensional Langevin equation is solved to describe the fission dynamics. Charge equilibration at scission and de-excitation by neutron evaporation of the primary fragments after scission is investigated. The model describes various observables, including fission-fragment mass, charge, and kinetic energy yields, as well as post-scission neutron multiplicities and, most importantly, their correlations, which are crucial to unravel the complexity of the fission process. The parameters of the dynamical model were tuned to reproduce experimental data obtained from thermal neutron-induced fission of $^{235}$ U, which allows us to discuss the transition from asymmetric to symmetric fission along the Fm isotopic chain.
nucl-thnucl-exActa Phys.Polon.B(2023)·2 citations
09
Scissors mode in transuranium elements
E. B. Balbutsev · I. V. Molodtsova
The scissors mode is investigated in the actinides region, including even-even superheavy nuclei up to $^{256}$ No, within the Time Dependent Hartree-Fock-Bogoliubov (TDHFB) approach. The solution of TDHFB equations by the Wigner Function Moments (WFM) method predicts a splitting of the scissors mode into three intermingled branches due to spin degrees of freedom. Both the calculated energy centroid and integrated $M 1$ strength in $^{254}$ No are in good agreement with the results of recent measurements performed by the Oslo method. The energy centroids and summed $B (M 1)$ values for others transuranium nuclides are predicted. The calculations are performed also for $^{232}$ Th and $^{236, 238}$ U isotopes using an updated compilation of deformation parameters. The results are compared with that obtained previously by WFM theory and with the latest experimental data. Progress has been achieved in theoretical understanding of the origins of double-humped structure of scissors spectrum observed in the Actinides.
nucl-thEPJA(2024)·6 citations
10
Suppression of the elastic scattering cross section for 17Ne + 208Pb system
Kyoungsu Heo · Myung-Ki Cheoun · Ki-Seok Choi · K. S. Kim · W. Y. So
We investigated the elastic scattering, inelastic scattering, breakup reaction, and total fusion reactions of 17Ne + 208Pb system using the optical model (OM) and a coupled channel (CC) approaches. The aim of this study is to elucidate the suppress of the elastic cross-section that is invisible in proton-rich nuclei such as 8B and 17F projectiles but appears in neutron-rich nuclei such as 11Li and 11Be projectiles. The results revealed that this suppression was caused mainly by the nuclear interaction between the projectile and target nucleus rather than the strong Coulomb interaction observed in neutron-rich nuclei and the contributions of Coulomb excitation interaction due to two low-lying E2 resonance states are relatively small. From the simultaneous chi-square analysis of the 17Ne + 208Pb system, we can infer a strong suppression effect in the elastic scattering cross-section due to the nuclear interaction between the projectile and target nucleus, rather than the Coulomb interaction as observed in neutron-rich nuclei. Also, the contribution of the direct reaction, comprising the inelastic scattering and breakup reaction cross-sections, accounted for almost half of the total reaction. Finally, we perform the CC calculation using the parameters obtained from our OM calculation but our CC calculations could not explain the 15O production cross section.
nucl-thPRC(2024)·4 citations
11
Generator coordinate method for nuclear octupole excitations: status and perspectives
E. F. Zhou · J. M. Yao
Strong octupole correlations have been observed in the low-lying states of atomic nuclei across various mass regions. In this review, we provide an overview of Beyond Mean-Field (BMF) studies of nuclear octupole collective motions with Generator Coordinate Method (GCM) in combination with quantum-number projections that are implemented to restore the broken symmetries in nuclear mean-field states. We highlight recent developments within this framework and their applications to excitation spectra and electromagnetic transition rates in octupole-shaped nuclei and hypernuclei. We discuss the novel phenomena of nucleon clustering in light nuclei. Additionally, we explore the phase transition from octupole vibrations to rotational motions as spin increases in heavy nuclei. Lastly, we examine the status and future prospects of studies on octupole deformation effects in nuclear Schiff moments. These studies, along with the upper limits of atomic Electric Dipole Moment (EDM), impose stringent constraints on beyond-standard-model time-reversal-violating nucleon-nucleon interactions.
nucl-thnucl-exIJMPE(2023)·9 citations
12
Crossover equation of state based on color-molecular-dynamics
Nobutoshi Yasutake🇯🇵 · Toshiki Maruyama🇯🇵
The equation of State for dense matter is studied with color molecular dynamics, in which hadron matter and quark matter are automatically distinguished only from quark color state. The quark-quark interactions are optimized to be consistent with saturation properties: symmetric energy, $L -$ parameter, and incompressibility around nuclear density. In the calculations, the degrees of freedom of colors are solved at each numerical step, although the flavors are fixed as up or down quarks. The resultant mass-radius relations also satisfy the observational constraints such as the gravitational wave observations, NICER, and ``{\it the two-solar mass observations}" of neutron stars. In this model with the allowed parameter range, deconfined quark matter appears in the core of neutron stars via crossover. Although the current constraints from the observations are not enough to conclude whether quark matter appears at high-density region, our method would help to understand high-density material properties inside neutron stars in the future.
nucl-thPRD(2024)·6 citations
13
Probe nuclear structure using the anisotropic flow at the Large Hadron Collider
Zhiyong Lu · Mingrui Zhao · Jiangyong Jia · You Zhou
Recent studies have shown that the shape and radial profile of the colliding nuclei have strong influences on the initial condition of the heavy ion collisions and the subsequent development of the anisotropic flow. Using A Multi-Phase Transport model (AMPT) model, we investigated the impact of nuclear quadrupole deformation $β_{2}$ and nuclear diffuseness $a_{0}$ of $^{129}$ Xe on various of flow observables in Xe--Xe collisions at $\sqrtnn =$ 5.44 TeV. We found that $β_{2}$ has a strong influence on central collisions while $a_{0}$ mostly influences the mid-central collisions. The relative change of flow observables induced by a change in $β_{2}$ and $a_{0}$ are also found to be insensitive to the values of parameters controlling the strength of the interaction among final state particles. Our study demonstrates the potential for constraining the initial condition of heavy ion collisions using future system scans at the LHC.
nucl-thnucl-exEPJA(2023)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE