arXiv subjects

Si-Na Wei

Publications and source records attributed to Si-Na Wei.

12 recordsLinked to original sources

arXiv2024

Shedding light on the pion production in heavy-ion collisions and application into the neutron star matter properties

Within the framework of the quantum molecular dynamics transport model, the pion production and constraint of the high-density symmetry energy in heavy-ion collisions near threshold energy have been thoroughly investigated. The energy conservation in the decay of resonances and reabsorption of pions as well as in the inelastic nucleon-nucleon and nucleon-resonance collisions are taken into account. The isospin diffusion in the low-density region (0.2$ρ_{0}$ - 0.8$ρ_{0}$) and high-density region (1.2$ρ_{0}$ - 1.8$ρ_{0}$) is investigated by analyzing the spectra of neutron/proton and $π^{-}/π^{+}$ ratios in the isotopic reactions of $^{132}$Sn + $^{124}$Sn and $^{108}$Sn + $^{112}$Sn at the incident energy of 270 MeV/nucleon, in which the symmetry energy manifests the opposite effect in the different density domain. The controversial conclusion of the $π^{-}/π^{+}$ ratio for constraining the high-density symmetry energy by different transport models with the FOPI data has been clarified. A soft symmetry energy with the slope parameter of $L(ρ_{0}) = 42\pm 25$ MeV by using the standard error analysis within the range of $1σ$ is obtained by analyzing the experimental data from the S$π$RIT collaboration. The neutron stars with the maximal mass of 2 $M_{\odot}$ and radius of 11-13 km are obtained with the constrained symmetry energy.

nucl-th↗

arXiv2024

Correlation of the hyperon potential stiffness with hyperon constituents in neutron stars and heavy-ion collisions

The breaking of SU(6) symmetry to a more general flavor SU(3) symmetry could serve as a potential explanation for the "hyperon puzzle" of neutron stars by adjusting the hyperon potentials. Specifically, when the soft relativistic mean-field (RMF) $Λ$ hyperon potentials fall within the domains of chiral SU(3) interactions NLO13 with two-body forces, the maximum mass of neutron stars is expected to be lower than 2.0 $M_\odot$, whereas it can exceed $2.0M_\odot$ if the RMF $Λ$ hyperon potentials are sufficiently stiff to be consistent with those from chiral SU(3) interactions NLO13 with three-body forces. In our investigation involving these two types of $Λ$ hyperon potentials, we explore how the hyperon yields and flows are affected in heavy-ion collisions. We find that the inclusion of hyperon potentials results in better agreement of the $Λ$ directed flows with data but without clear differentiation in the stiffness of the hyperon potentials. Similarly negligent is the disparity in the rapidity distributions of the $Λ$ collective flows predicted by the stiff and soft hyperon potentials. In contrast, the $Λ$ collective flows beyond the central rapidity region turn out to be sensitive to the stiffness of the RMF equation of state (EOS) with the preference of a soft RMF EOS to a stiff one. Notably, the transverse momentum distributions of $Λ$ hyperon production are sensitive to both the stiffness of the RMF EOS and $Λ$ hyperon potential at high transverse momenta.

nucl-th↗

arXiv2023

Pion production in intermediate-energy heavy-ion collisions with a relativistic quantum molecular dynamics model

The relativistic mean field approach by distinguishing \com{the slope of symmetry energy} is implemented into the Lanzhou quantum molecular dynamics transport model (LQMD.RMF). The collective flows in the isotopic nuclear reactions are systematically investigated by the relativistic quantum molecular dynamics model \com{with various slopes of symmetry energy}. The structure of the directed and elliptic flows is consistent with the results of the nonrelativistic transportation of nucleon system. \com{The directed flow difference between free neutrons and protons appears in the midrapidity region. The transverse momentum spectra of $π^+$ production is close to each other in the nearly symmetric $^{108}\mathrm{Sn} + ^{112}\mathrm{Sn}$ system and the neutron-rich $^{132}\mathrm{Sn} + ^{124}\mathrm{Sn}$ system. However, since there are more neutron-neutron scatterings in neutron-rich system, the transverse momentum spectra of $π^-$ production in the neutron-rich system are higher than one in the nearly symmetric system. For a given reaction system, the transverse momentum spectra of $π^+$ and $π^-$ production are independent on the stiffness of symmetry energy. This leads to the fact that the single ratio and the double ratio are independent on the stiffness of symmetry energy. Moreover, the double ratio without the $π$-nucleon potential decreases with increasing the transverse momentum. However, the double ratio with the inclusion of $π$ potential increases with increasing the transverse momentum.

nucl-th↗

arXiv2023

Strong correlation of the neutron star core-crust transition density with the $σ$-meson mass via vacuum polarization

We study the neutron star core-crust transition density $ρ_t$ with the inclusion of the vacuum polarization in the dielectric function in the nonlinear relativistic Hartree approach (RHAn). It is found that the strong correlation between the $ρ_{t}$ and the scalar meson mass $m_σ$ strikingly overwhelms the uncertainty of the nuclear equation of state in the RHAn models, in contrast to the usual awareness that $ρ_{t}$ is predominantly sensitive to the isovector nuclear potential and symmetry energy. The accurate extraction of $ρ_{t}$ through the future gravitational wave measurements can thus provide a strong constraint on the longstanding uncertainty of $m_σ$, which is of significance to better infer the vacuum property. As an astrophysical implication, it suggests that the correlation between $ρ_t$ and $m_σ$ is very favorable to reconcile the difficulty in reproducing the large crustal moment of inertia for the pulsar glitches with the well constrained symmetry energy.

nucl-th↗

arXiv2021

Nuclear potentials relevant to the symmetry energy in chiral models

We employ the extended Nambu-Jona-Lasinio, linear-$σ$ models, and the density-dependent model with chiral limits to work out the mean fields and relevant properties of nuclear matter. To have the constraint from the data, we reexamine the Dirac optical potentials and symmetry potential based on the relativistic impulse approximation (RIA). Unlike the extended NJL and the density-dependent models with the chiral limit in terms of the vanishing scalar density, the extended linear-$σ$ model with a sluggish changing scalar field loses the chiral limit at the high density end. The various scalar fields can characterize the different Schrödinger-equivalent potentials and kinetic symmetry energy in the whole density region and the symmetry potential in the intermediate density region. The drop of the scalar field due to the chiral restoration results in a clear rise of the kinetic symmetry energy. The chiral limit in the models gives rise to the softening of the symmetry potential and thereof the symmetry energy at high densities.

nucl-th↗

arXiv2021

Symmetry energy and neutron star properties in the saturated Nambu-Jona-Lasinio model

In this work, we adopt the Nambu-Jona-Lasinio (NJL) model that ensures the nuclear matter saturation properties to study the density dependence of the symmetry energy. With the interactions constrained by the chiral symmetry, the symmetry energy shows novel characters different from those in conventional mean-field models. First, the negative symmetry energy at high densities that is absent in relativistic mean-field (RMF) models can be obtained in the RMF approximation by introducing a chiral isovector-vector interaction, although it would be ruled out by the neutron star (NS) stability. Second, with the inclusion of the isovector-scalar interaction the symmetry energy exhibits a general softening at high densities even for the large slope parameter of the symmetry energy. The NS properties obtained in the present NJL model can be in accord with the observations. The NS maximum mass obtained with various isovector-scalar couplings and momentum cutoffs is well above the $2M_\odot$, and the NS radius obtained well meets the limits extracted from recent measurements. In particular, the significant reduction of the canonical NS radius occurs with the moderate decrease of the slope of the symmetry energy.

nucl-th↗

arXiv2021

Symmetry potentials and in-medium nucleon-nucleon cross sections within the Nambu-Jona-Lasinio model in relativistic impulse approximation

In the relativistic impulse approximation (RIA), we study symmetry potentials and in-medium nucleon-nucleon (NN) cross sections with the Nambu-Jona-Lasinio (NJL) model that features chiral symmetry. The chiral symmetry that plays a fundamental role in the nonperturbative physics in the strong interaction is anticipated to add restrictive effects on the symmetry potentials and in-medium NN cross sections. For comparison, we also perform the study with the usual relativistic mean-field (RMF) model. The numerical results with the NJL and RMF models are similar at saturation density and below, since a priori fit was made to saturation properties. With the increase of nuclear density, the chiral symmetry starts to be restored partially in the NJL model, resulting in the explicit fall of the scalar density. In a large energy span, the symmetry potential acquires a significant rise for the partial restoration of the chiral symmetry, compared to the one with the RMF model. It is found that the in-medium NN cross sections in the RIA with the NJL and RMF models both increase with the density in the energy region interested in this study, whereas those with the NJL model increase sharply as long as a clear chiral symmetry restoration takes place. The different tendency of observables in density can be transmitted to the different energy dependence in the RIA. The NJL model is shown to have characteristic energy-dependent symmetry potentials and NN cross sections beyond saturation point, apart from the RMF models.

nucl-th↗

arXiv2019

Level inversion in kaonic nuclei and the high-density nuclear equation of state

It is very difficult for any nuclear model to pin down the saturation property and high-density equation of state (EOS) simultaneously because of high nonlinearity of the nuclear many-body problem. In this work, we propose, for the first time, to use the special property of light kaonic nuclei to characterize the relation between saturation property and high-density EOS. With a series of relativistic mean-field models, this special property is found to be the level inversion between orbitals $2S_{1/2}$ and $1D_{5/2}$ in light kaonic nuclei. This level inversion can serve as a theoretical laboratory to group the incompressibility at saturation density and the EOS at supra-normal densities simultaneously.

nucl-th↗

arXiv2018

Ground-state properties of light kaonic nuclei signaling symmetry energy at high densities

A sensitive correlation between the ground-state properties of light kaonic nuclei and the symmetry energy at high densities is constructed under the framework of relativistic mean-field theory. Taking oxygen isotopes as an example, we see that a high-density core is produced in kaonic oxygen nuclei, due to the strongly attractive antikaon-nucleon interaction. It is found that the $1S_{1/2}$ state energy in the high-density core of kaonic nuclei can directly probe the variation of the symmetry energy at supranormal nuclear density, and a sensitive correlation between the neutron skin thickness and the symmetry energy at supranormal density is established directly. Meanwhile, the sensitivity of the neutron skin thickness to the low-density slope of the symmetry energy is greatly increased in the corresponding kaonic nuclei. These sensitive relationships are established upon the fact that the isovector potential in the central region of kaonic nuclei becomes very sensitive to the variation of the symmetry energy. These findings might provide another perspective to constrain high-density symmetry energy, and await experimental verification in the future.

nucl-th↗

arXiv2017

The resonant heating of heavy water solutions under the terahertz pulse irradiation

The heating effect of terahertz pulse with various frequencies and intensities on the heavy water solution is investigated using the molecular dynamics simulation. Resonant absorptions are found for both heavy water and light water, but at a different resonant frequency which is about 16 THz for heavy water and 21 THz for light water. This resonant phenomenon can be explained perfectly by the collective rotational modes that may release water molecules from hydrogen bonding. The findings not only illustrate the heating mechanism of heavy water solution under the terahertz pulse irradiation, but also demonstrate a novel difference between light water and heavy water that could have potential applications.

physics.chem-ph↗

arXiv2016

Equation of state and hybrid star properties with the weakly interacting light U-boson in relativistic models

It has been a puzzle whether quarks may exist in the interior of massive neutron stars, since the hadron-quark phase transition softens the equation of state (EOS) and reduce the neutron star (NS) maximum mass very significantly. In this work, we consider the light U-boson that increases the NS maximum mass appreciably through its weak coupling to fermions. The inclusion of the U-boson may thus allow the existence of the quark degrees of freedom in the interior of large mass neutron stars. Unlike the consequence of the U-boson in hadronic matter, the stiffening role of the U-boson in the hybrid EOS is not sensitive to the choice of the hadron phase models. In addition, we have also investigated the effect of the effective QCD correction on the hybrid EOS. This correction may reduce the coupling strength of the U-boson that is needed to satisfy NS maximum mass constraint. While the inclusion of the U-boson also increases the NS radius significantly, we find that appropriate in-medium effects of the U-boson may reduce the NS radii significantly, satisfying both the NS radius and mass constraints well.

nucl-th↗

arXiv2014

Relativistic symmetry breaking in light kaonic nuclei

As the experimental data from kaonic atoms and $K^{-}N$ scatterings imply that the $K^{-}$-nucleon interaction is strongly attractive at saturation density, there is a possibility to form $K^{-}$-nuclear bound states or kaonic nuclei. In this work, we investigate the ground-state properties of the light kaonic nuclei with the relativistic mean field theory. It is found that the strong attraction between $K^{-}$ and nucleons reshapes the scalar and vector meson fields, leading to the remarkable enhancement of the nuclear density in the interior of light kaonic nuclei and the manifest shift of the single-nucleon energy spectra and magic numbers therein. As a consequence, the pseudospin symmetry is shown to be violated together with enlarged spin-orbit splittings in these kaonic nuclei.

nucl-th↗