arXiv subjects

Wei Zuo

Publications and source records attributed to Wei Zuo.

At least 55 records · Page 3Linked to original sources

arXiv2019

Probing nuclear bubble configuration by proton induced reaction

In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, nuclear bubble configuration in the hypothetical $^{48}$Si nucleus is studied by proton induced central reaction at an incident beam energy of 0.8 GeV/nucleon. It is found that along the beam direction more energetic protons are emitted with bubble configuration in the target. In the forward angles, compared with the case without bubble configuration, less scattered energetic protons are emitted with bubble configuration in the target. We thus provide a new way to probe the bubble configuration in nuclei.

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arXiv2019

Understanding the $η_cρ$ decay mode of $Z_c^{(\prime)}$ via the triangle loop mechanism

Recently, the BESIII Collaboration reported a new measurement of the $η_c ρ$ decay mode of $Z_c^{(\prime)}$, which motivated us to study the inner structure of $Z_c^{(\prime)}$ via investigating the hidden charm decays of these two $Z_c$ states. We consider the {triangle loop mechanism} contribution in the hidden charm decays of $Z_c^{(\prime)}$. Our estimations indicate that the triangle loop mechanism plays an important role in the decays of the $Z_c^{(\prime)}$, where our results are in agreement with the experimental observations in a reasonable parameter range. Furthermore, we point out that the $Z_c^{(\prime)}$ can be interpreted as the hadronic molecules, while the tetraquark scenario is less favored.

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arXiv2018

Proton spectral functions in finite nuclei based on the extended Brueckner-Hartree-Fock approach

We have calculated the proton spectral functions in finite nuclei based on the local density approximation where the properties of finite nuclei and nuclear matter are calculated by the Skyrme-Hartree-Fock method and the extended Brueckner-Hartree-Fock approach, respectively. The scaled spectral function from our calculation is in good agreement with experimental results at small momenta while the difference between them becomes apparent at high momenta. Besides, a target dependence of the scaled proton spectral function is also obtained in our calculation as was observed in experiment. A further investigation indicates that the proportion of the high density region of the proton has a significant contribution to this target-dependent behavior since the spectral function in asymmetric nuclear matter increases significantly as a function of density.

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arXiv2018

Effects of the initialization of nucleon momentum in heavy-ion collisions at medium energies

Based on the Isospin-dependent transport model Boltzmann-Uehling-Uhlenbeck (IBUU), effects of the difference of the high momentum tails (HMTs) of nucleon momentum distribution in colliding nuclei on some isospin-sensitive observables are studied in the $^{197}\rm {Au}+^{197}\rm {Au}$ reactions at incident beam energy of 400 MeV/nucleon. It is found that the nucleon transverse and elliptic flows, the free neutron to proton ratio at low momenta are all less sensitive to the specific form of the HMT, while the free neutron to proton ratio at high momenta and the yields of $π^{-}$ and $π^{+}$ as well as the $π^{-}/π^{+}$ ratio around the Coulomb peak are sensitive to the specific form of the HMT. Combining the present studies with the experimental measurements at rare-isotope reaction facilities worldwide, one may get more insights into the nuclear short-range correlations in heavy nuclei or nuclear matter.

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arXiv2018

Coulomb Excitation of Deuteron in Peripheral Collisions with a Heavy Ion

We develop an ab initio, non-perturbative, time-dependent Basis Function (tBF) method to solve the nuclear structure and scattering problems in a unified manner. We apply this method to a test problem: the Coulomb excitation of a trapped deuteron by an impinging heavy ion. The states of the deuteron system are obtained by the ab initio nuclear structure calculation implementing a realistic inter-nucleon interaction with a weak external trap to localize the center of mass and to discretize the continuum. The evolution of the internal state of the deuteron system is directly solved using the equation of motion for the scattering. We analyze the excitation mechanism of the deuteron system by investigating its internal transition probabilities and observables as functions of the exposure time and the incident speed. In this investigation, the dynamics of the Coulomb excitation are revealed by the time evolution of the system's internal charge distribution.

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arXiv2018

Probing the density dependence of the symmetry energy by nucleon flow

In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, sensitive regions of some nucleon observables to the nuclear symmetry energy are studied. It is found that the symmetry energy sensitive observable n/p ratio in the $^{132}$Sn+$^{124}$Sn reaction at 0.3 GeV/nucleon in fact just probes the density-dependent symmetry energy below the density of $1.5ρ_0$ and effectively probes the density-dependent symmetry energy around or somewhat below the saturation density. Nucleon elliptic flow can probe the symmetry energy from the low-density region to the high-density region when changing the incident beam energies from 0.3 to 0.6 GeV/nucleon in the semi-central $^{132}$Sn+$^{124}$Sn reaction. And nucleon transverse and elliptic flows in the semi-central $^{197}$Au+$^{197}$Au reaction at 0.6 GeV/nucleon are more sensitive to the high-density behavior of the nuclear symmetry energy. One thus concludes that nucleon observables in the heavy reaction system and with higher incident beam energy are more suitable to be used to probe the high-density behavior of the symmetry energy. The present study may help one to get more specific information about the density-dependent symmetry energy from nucleon flow observable in heavy-ion collisions at intermediate energies.

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arXiv2015

Effect of Delta potential on the pion-/pion+ ratio in heavy-ion collisions at intermediate energies

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport model, effects of $Δ$ resonance potential on the free n/p and $π^-/π^+$ ratios in the central collision of $^{197}Au+^{197}Au$ at beam energies of 200 and 400 MeV/A are studied. It is found that the effect of $Δ$ potential on the ratio of pre-equilibrium free $n/p$ is invisible. The effect of $Δ$ isovector potential on the kinetic energy integrating ratio of $π^-/π^+$ may be observable only at lower incident beam energies and with stiffer symmetry energy. The strength of the $Δ$ isoscalar potential affects the height of the $π^-/π^+$ ratio around the Coulomb peak but does not affect the kinetic energy integrating ratio of $π^-/π^+$. In heavy-ion collisions at intermediate energies, relating to the question of non-conservation of energy on $Δ$ or $π$ productions, one can replace the $Δ$ potential by nucleon isoscalar potential especially a soft symmetry energy is employed.

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arXiv2015

Effects of pion potential and nuclear symmetry energy on the $π^{-}/π^{+}$ ratio in heavy-ion collisions at beam energies around the pion production threshold

Within the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport model, we studied the effects of the pion potential and the symmetry energy on the pion production in the central $^{197}Au+^{197}Au$ collisions around the pion production threshold. It is found that the pion potential has opposite effects on the value of $π^-/π^+$ ratio at low and high pion energies. The effect of the pion potential on the total $π^-/π^+$ ratio becomes larger in heavy-ion collisions at beam energies below the pion production threshold. And at beam energies below the pion production threshold, with the pion potential, the effect of the symmetry energy on the $π^-/π^+$ ratio becomes smaller compared with that above the pion production threshold.

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arXiv2015

Symmetry energy at subsaturation densities and the neutron skin thickness of 208Pb

The mass-dependent symmetry energy coefficients $a_{sym}(A)$ has been extracted by analysing the heavy nuclear mass differences reducing the uncertainties as far as possible in our previous work. Taking advantage of the obtained symmetry energy coefficient $a_{sym}(A)$ and the density profiles obtained by switching off the Coulomb interaction in $^{208}\text{Pb}$, we calculated the slope parameter $L_{0.11}$ of the symmetry energy at the density of $0.11\text{fm}^{-3}$. The calculated $L_{0.11}$ ranges from 40.5 MeV to 60.3 MeV. The slope parameter $L_{0.11}$ of the symmetry energy at the density of $0.11\text{fm}^{-3}$ is also calculated directly with Skyrme interactions for nuclear matter and is found to have a fine linear relation with the neutron skin thickness of $^{208}\text{Pb}$, which is the difference of the neutron and proton rms radii of the nucleus. With the linear relation the neutron skin thickness $ ΔR_{np} $ of $^{208}\text{Pb}$ is predicted to be 0.15 - 0.21 fm.

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arXiv2015

Constraints on neutron skin thickness in 208Pb and density-dependent symmetry energy

Accurate knowledge about the neutron skin thickness $ΔR_{np}$ in $^{208}$Pb has far-reaching implications for different communities of nuclear physics and astrophysics. Yet, the novel Lead Radius Experiment (PREX) did not yield stringent constraint on the $ΔR_{np}$ recently. We employ a more practicable strategy currently to probe the neutron skin thickness of $^{208}$Pb based on a high linear correlation between the $ΔR_{np}$ and $J-a_{\text{sym}}$, where $J$ and $a_{\text{sym}}$ are the symmetry energy (coefficient) of nuclear matter at saturation density and of $^{208}$Pb. An accurate $J-a_{\text{sym}}$ thus places a strong constraint on the $ΔR_{np}$. Compared with the parity-violating asymmetry $A_{\text{PV}}$ in the PREX, the reliably experimental information on the $J-a_{\text{sym}}$ is much more easily available attributed to a wealth of measured data on nuclear masses and on decay energies. The density dependence of the symmetry energy is also well constrained with the $J-a_{\text{sym}}$. Finally, with a `tomoscan' method, we find that one just needs to measure the nucleon densities in $^{208}$Pb starting from $R_{m} = 7.61\pm0.04$ fm to obtain the $ΔR_{np}$ in hadron scattering experiments, regardless of its interior profile that is hampered by the strong absorption.

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arXiv2015

FFLO state with angle dependent Gap in Asymmetric Nuclear Matter

We consider the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state with an angle dependent-gap (ADG) for the arbitrary angle θ_0 between the direction of the Cooper pair momentum and the symmetry axis of the ADG in asymmetric nuclear matter. We find two kinds of locally stable states, i.e., the FFLO-ADG-orthogonal and FFLO-ADG-parallel states, which correspond to θ_0=π/2 and θ_0=0, respectively. Furthermore, the-FFLO-ADG-orthogonal state is located at small asymmetry, whereas the FFLO-ADG-parallel state is favored for large asymmetry. The critical isospin asymmetry α_c, where the superfluid vanishes, is enhanced largely by considering the Cooper pair momentum with an ADG.

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arXiv2014

Normal or abnormal isospin-fractionation as a qualitative probe of nuclear symmetry energy at supradensities

Within two different frameworks of isospin-dependent transport model, effect of nuclear symmetry energy at supradensities on the isospin-fractionation (IsoF) was investigated. With positive/negative symmetry potential at supradensities (i.e., values of symmetry energy increase/decrease with density above saturation density), for energetic nucleons, the value of neutron to proton ratio of free nucleons is larger/smaller than that of bound nucleon fragments. Compared with extensively studied quantitative observables of nuclear symmetry energy, the normal or abnormal isospin-fractionation of energetic nucleons can be a qualitative probe of nuclear symmetry energy at supradensities.

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arXiv2014

Effects of nuclear symmetry energy and in-medium NN cross section in heavy-ion collisions at beam energies below the pion production threshold

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU04) transport model, we explored effects of in-medium $NN$ elastic scattering cross section and nuclear symmetry energy on the sub-threshold pion production in $^{132}Sn+^{124}Sn$ reaction. We find that with decrease of incident beam energy, effects of in-medium $NN$ elastic scattering cross section on the $π^{-}/π^{+}$ ratio are larger than that of the symmetry energy although the latter may be also larger. While keeping the effect of symmetry energy, the double ratio of $π^{-}/π^{+}$ from neutron-rich and neutron-poor reaction systems (with the same mass number of system) $^{132}Sn+^{124}Sn$ and $^{128}Pm+^{128}Pm$ almost fully cancels out the effects of in-medium $NN$ elastic scattering cross section.

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arXiv2014

Three-body force effect on the properties of nuclear matter under the gap and continuous choices within the BHF approach

We have calculated and compared the three-body force effects on the properties of nuclear matter under the gap and continuous choices for the self-consistent auxiliary potential within the Brueckner-Hartree-Fock approach by adopting the Argonne $V18$ and the Bonn B two-body potentials plus a microscopic three-body force (TBF). The TBF provides a strong repulsive effect on the equation of state of nuclear matter at high densities for both the gap and continuous choices. The saturation point turns out to be much closer to the empirical value when the continuous choice is adopted. In addition, the dependence of the calculated symmetry energy upon the choice of the self-consistent auxiliary potential is discussed.

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arXiv2014

Effect of tensor force on density dependence of symmetry energy within the BHF Framework

The effect of tensor force on the density dependence of nuclear symmetry energy has been investigated within the framework of the Brueckner-Hartree-Fock approach. It is shown that the tensor force manifests its effect via the tensor $^3SD_1$ channel. The density dependence of symmetry energy $E_{sym}$ turns out to be determined essentially by the tensor force from the $π$ meson and $ρ$ meson exchanges via the $^3SD_1$ coupled channel. Increasing the strength of the tensor component due to the $ρ$-meson exchange tends to enhance the repulsion of the equation of state of symmetric nuclear matter and leads to reduction of symmetry energy. The present results confirm the dominant role played by the tensor force in determining nuclear symmetry energy and its density dependence within the microscopic BHF framework.

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arXiv2014

Density-dependent symmetry energy at subsaturation densities from nuclear mass differences

We extract the mass-dependent symmetry energy coefficients $a_{\text{sym}}({A})$ with the nuclear mass differences reducing the uncertainties as far as possible. The estimated $a_{\text{sym}}({A})$ of $^{208}\text{Pb}$ is $22.4\pm 0.3 $ MeV, which is further used to analyze the density-dependent nuclear matter symmetry energy at subsaturation densities. The slope parameter of the symmetry energy at the saturation density $ρ_{0}$ is $L=50.0\pm15.5$ MeV. Furthermore, it is found that, at the density of $ρ=0.69ρ_{0}=0.11$fm$^{-3}$, the symmetry energy $S(ρ=0.11\text{fm}^{-3})=25.98\pm0.01$ MeV and the correspondingly slope parameter is $L=49.6\pm6.2$ MeV, which are consistent with other independent analysis.

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arXiv2013

Decomposition of EOS of Asymmetric Nuclear Matter into Different Spin-isospin Channels

We investigate the equation of state of asymmetric nuclear matter and its isospin dependence in various spin-isospin $ST$ channels within the framework of the Brueckner-Hartree-Fock approach extended to include a microscopic three-body force (TBF). It is shown that the potential energy per nucleon in the isospin-singlet T=0 channel is mainly determined by the contribution from the tensor SD coupled channel. At high densities, the TBF effect on the isospin-triplet T=1 channel contribution turns out to be much larger than that on the T=0 channel contribution. At low densities around and below the normal nuclear matter density, the isospin dependence is found to come essentially from the isospin-singlet SD channel and the isospin-triplet T=1 component is almost independent of isospin-asymmetry. As the density increases, the T=1 channel contribution becomes sensitive to the isospin-asymmetry and at high enough densities its isospin-dependence may even become more pronounced than that of the T=0 contribution. The present results may provide some microscopic constraints for improving effective nucleon-nucleon interactions in nuclear medium and for constructing new functionals of effective nucleon-nucleon interaction based on microscopic many-body theories.

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arXiv2013

Single particle potentials of asymmetric nuclear matter in different spin-isospin channels

We investigate the neutron and proton single particle (s.p.) potentials of asymmetric nuclear matter and their isospin dependence in various spin-isospin $ST$ channels within the framework of the Brueckner-Hartree-Fock approach. It is shown that in symmetric nuclear matter, the s.p. potentials in both the isospin-singlet T=0 channel and isospin-triplet T=1 channel are essentially attractive, and the magnitudes in the two different channels are roughly the same. In neutron-rich nuclear matter, the isospin-splitting of the proton and neutron s.p. potentials turns out to be mainly determined by the isospin-singlet T=0 channel contribution which becomes more attractive for proton and more repulsive for neutron at higher asymmetries.

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