arXiv subjects

Zhao-Qing Feng

Publications and source records attributed to Zhao-Qing Feng.

At least 37 records · Page 2Linked to original sources

arXiv2022

Production cross-sections of new superheavy elements with Z = 119-120 in fusion-evaporation reactions

We have calculated production cross sections of new superheavy elements with atomic number Z=119,120 in the fusion-evaporation reactions of $^{48}$Ca+$^{252}$Es, $^{48}$Ca+$^{257}$Fm, $^{49}$Sc+$^{252}$Es, $^{49}$Sc+$^{251}$Cf, $^{50}$Ti+$^{247}$Bk, $^{50}$Ti+$^{251}$Cf, $^{51}$V+$^{247}$Cm, $^{51}$V+$^{247}$Cf, $^{54}$Cr+$^{243}$Am, $^{54}$Cr+$^{247}$Cm, $^{56}$Mn+$^{244}$Pu, $^{56}$Mn+$^{243}$Am, $^{60}$Fe+$^{237}$Np, $^{60}$Fe+$^{244}$Pu, $^{61}$Co+$^{238}$U, $^{61}$Co+$^{237}$Np, $^{64}$Ni+$^{231}$Pa, $^{64}$Ni+$^{238}$U, $^{65}$Cu+$^{232}$Th, $^{65}$Cu+$^{231}$Pa, and $^{68}$Zn+$^{232}$Th within the dinuclear system model systematically. The inner fusion barriers have been extracted from the driving potential or potential energy surface which could be used to predict the relative fusion probability roughly. The influence of mass asymmetry of the colliding partners on the production of new superheavy elements (SHE) has been investigated systematically. It is found that fusion probability increase along with the increasing mass asymmetry of colliding systems. The Ti-induced reactions have the largest cross-sections of the new SHE. The dependence of production cross-sections of new superheavy elements on the isospin of projectile nuclei has been discussed. The new SHE of $^{289-295}$119 has been predicted as the synthesis cross sections around serval picobarns in the $^{46,48,50,52}$Ti-induced reactions. Production cross-section of the element of $^{295}$120 has been evaluated as large as 1 picobarn in the reactions $^{46}$Ti ($^{251}$Cf, 2n) $^{295}$120 at $E^*$ = 26 MeV. The optimal projectile-target combinations and beam energies for producing new SHE with atomic number Z=119-120 are proposed for the forthcoming experiments.

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arXiv2022

Prediction for the synthesis cross sections of new moscovium isotopes in fusion-evaporation reactions

In the framework of the dinuclear system model, the synthesis mechanism of the superheavy nuclides with atomic number $Z=112, 114, 115$ in the reactions of projectiles $^{40,48}$Ca bombarding on targets $^{238}$U, $^{242}$Pu, and $^{243}$Am at a wide incident energies (excitation energy from 0-100 MeV) have been investigated systematically. Based on the available experimental excitation functions, the dependence of calculated synthesis cross sections on collision orientations has been studied thoroughly. The TKEs of these collisions with the fixed collision orientation show its orientation dependence which can be used to predict the tendency of kinetic energy diffusion. The TKEs are dependent on incident energies which have been discussed. The method of Coulomb barrier distribution function has been applied in our calculations which could treat all of the collision orientations from the tip-tip to side-side approximately. The calculations of excitation functions of $^{48}$Ca + $^{238}$U, $^{48}$Ca + $^{242}$Pu, and $^{48}$Ca + $^{243}$Am have a nice agreement with the available experimental data. The isospin effect of projectiles on production cross sections of moscovium isotopes and the influence of entrance channel effect on the synthesis cross sections of superheavy nuclei have been discussed. The synthesis cross section of new moscovium isotopes $^{278-286}$Mc have been predicted as large as hundreds pb, in the fusion-evaporation reactions of $^{35,37}$Cl + $^{248}$Cf, $^{38,40}$Ar + $^{247}$Bk, $^{39,41}$K + $^{247}$Cm, $^{40,42,44,46}$Ca + $^{238}$Am, $^{45}$Sc + $^{242}$Pu, and $^{46,48,50}$Ti + $^{243}$Np, $^{51}$V + $^{238}$U at the excitation energy interval of 0-100 MeV.

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arXiv2022

Production of neutron-rich actinide nuclides in isobaric collisions via multinucleon transfer reactions

We have calculated the multinucleon transfer reactions of $^{208}$Os, $^{208}$Pt, $^{208}$Hg, $^{208}$Pb,$^{208}$Po, $^{208}$Rn, $^{208}$Ra,$^{132,136}$Xe bombarding on $^{232}$Th and $^{248}$Cm at Coulomb barrier energies within the dinuclear system model, systematically. The results are in good agreement with the available experimental data. Coulomb effect and shell effect on production of actinides in these reactions have been investigated thoroughly. Potential energy surface and total kinetic energy mass distributions in the reactions $^{208}$Hg, $^{208}$Pb and$^{208}$Po colliding on $^{248}$Cm and $^{232}$Th are calculated and analyzed, respectively. It is found that PES and TKE spectra manifest the fragment formation mechanism in the multinucleon transfer reactions. The isospin effect and shell effect are shown in PES and TKE. Production cross-sections of multinucleon transfer products are highly dependent on the isobar projectiles with mass number $A=208$. The isobar projectiles with larger N/Z ratios are favorable for creating the neutron-rich target-like fragments. The isobar projectiles with larger charge number induced products tend to shift to proton-rich region. Coulomb potential coupled to shell effect is shown in production cross-sections of actinide isotopes. Based on the radioactive projectiles induced reactions, we have predicted massive new actinide isotopes around nuclear drip lines, even could access the superheavy nuclei region.

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arXiv2022

Influence of entrance channel on production cross section of exotic actinides in multinucleon transfer reactions

Within the framework of the dinuclear system model, the influence of mass asymmetry and the isospin effect on the production of exotic actinides have been investigated systematically. The isotopic yields populate in multinucleon transfer reactions of Ca(48), Kr(86), Xe(136), and U(238) bombarding on Cm(248) are analyzed and compared to the available experimental data. Systematics on the production of unknown actinides from Ac to Lr via the available stable elements on the earth (from Ar to U) as projectiles-induced reactions with $^{232}$Th, $^{238}$U and $^{248}$Cm are investigated thoroughly. Potential energy surface and total kinetic energy distribution for the reaction system are calculated and can be used to predict the production cross-section trends. It is found that the heavier projectile leads to the wider isotopic chain distribution for the same target. The heavier target-based reactions prefer to produce plenty of exotic actinides through both mechanisms of deep-inelastic and quasi-fission reactions. Isospin relaxation plays a crucial role in the colliding process, resulting in actinide isotopic distribution tends to shift to the drip lines. Massive new actinides have been predicted at the level of nanobarn to millibarn. The optimal projectile-target combinations and beam energies were proposed for the forthcoming experiments.

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arXiv2022

Potential energy surface and formation of superheavy nuclei with the Skyrme energy-density functional

Within the framework of Skyrme energy-density functional theory, the nucleus-nucleus potential is calculated and potential energy surface is obtained with different effective forces for accurately estimating the formation cross sections of superheavy nuclei in massive fusion reactions. The width and height of the potential pocket are influenced by the Skyrme effective forces SkM, SkM$^{\ast}$, SkP, SIII, Ska and SLy4, which correspond to the different equation of state for the isospin symmetry nuclear matter. It is found that the nucleus-nucleus potential is associated with the collision orientation and Skyrme parameters. More repulsive nuclear potential is pronounced with increasing the incompressible modulus of nuclear matter. The available data in the fusion-evaporation reaction of $^{48}$Ca+$^{238}$U are nicely reproduced with the SkM$^{\ast}$ parameter by implementing into the dinuclear system model.

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arXiv2022

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.

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arXiv2022

Solar system constraints of a polymer black hole in loop quantum gravity

A new polymer black hole solution in loop quantum gravity was proposed recently. The difference between the polymer black hole and Schwarzschild black hole is captured by a quantum parameter $A$. In order to get the constraints on parameter $A$, we consider the observational constraints imposed on $A$ by using the Solar System experiments and calculate the deflection of light, Shapiro time delay, perihelion precession and obtain the effects associated with parameter $A$. Moreover, the parameterized post-Newtonian approach of this loop quantum gravity black hole was also carried out. It turns out the tightest constraint on $A$ can be improved to $0<A<4.0\times10^{-6}$.

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arXiv2022

Rare Isotope Formation in Complete Fusion and Multinucleon Transfer Reactions in Collisions of 48Ca +248Cm around Coulomb Barrier Energies

Within the framework of the dinuclear system model, the reaction mechanisms for synthesizing target-like isotopes from Bk to compound nuclei Lv are thoroughly investigated in complete and incomplete fusion reaction of $^{48}$Ca +$^{248}$Cm around Coulomb barrier energies. Production cross-section of $^{292,293}$Lv as a function of excitation energy in fusion-evaporation reactions and target-like isotopic yields in multinucleon transfer reactions are evaluated, in which a statistical approach is used to describe the decay process of excited nuclei. The available experimental data can be reproduced well with the model reasonably. The products of all possible formed isotopes in the dynamical pre-equilibrium process for collision partners at incident energy $E_{\rm lab}$ = 5.5 MeV/nucleon are exported, systematically. It is found that the quasi-fission fragments are dominant in the yields. The optimal pathway from the target to compound nuclei shows up along the valley of potential surface energy. The effective impact parameter of two colliding partners leading to compound nuclei is selected from head-on collision to semi-central collision with $L$ = 52 $\rm \hbar$. The timescale boundary between complete fusion and multinucleon transfer reactions is about 5.7$\times 10^{-21}$ s with effective impact parameters. Synthesis cross-section of unknown neutron-rich actinides from Bk to Rf have been predicted around several nanobarns.

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arXiv2021

Dynamics of light hypernuclei in collisions of $^{197}$Au+$^{197}$Au at GeV energies

The dynamics of light hypernuclei and nuclear clusters produced in $^{197}$Au+$^{197}$Au collisions has been investigated thoroughly with a microscopic transport model. All possible channels of hyperon production and transportation of hyperons in nuclear medium are implemented into the model. The light complex fragments are recognized with the Wigner density approach at the stage of freeze out in nuclear collisions. The isospin diffusion in the collisions is responsible for the neutron-rich cluster formation. The collective flows of nuclear clusters are consistent with the experimental data from FOPI collaboration. It is found that the influence of the hyperon-nucleon potential on the free hyperons is negligible, but available for the light hypernuclide formation. The directed and elliptic flows of $^{3}_Λ$H and $^{4}_Λ$H at incident energies of 2, 2.5, 3, 3.5 and 4 GeV/nucleon are investigated thoroughly and manifest the same structure with the nuclear clusters. The hypernuclear yields are produced in a wide rapidity and momentum regime with increasing the beam energy.

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arXiv2021

Systematics on production of superheavy nuclei $Z = 119-122$ in fusion-evaporation reactions

The fusion dynamics on the formation of superheavy nuclei is investigated thoroughly within the dinuclear system model. The Monte Carlo approach is implemented into the nucleon transfer process for including all possible orientations, at which the dinuclear system is assumed to be formed at the touching configuration of dinuclear fragments. The production cross sections of superheavy nuclei Cn, Fl, Lv, Ts and Og are calculated and compared with the available data from Dubna. The evaporation residue excitation functions in the channels of pure neutrons and charged particles are analyzed systematically. The combinations with $^{44}$Sc, $^{48,50}$Ti, $^{49,51}$V, $^{52,54}$Cr, $^{58,62}$Fe and $^{62,64}$Ni bombarding the actinide nuclides $^{238}$U, $^{244}$Pu, $^{248}$Cm, $^{247,249}$Bk, $^{249,251}$Cf, $^{252}$Es and $^{243}$Am are calculated for producing the superheavy elements with Z=119-122. It is found that the production cross sections sensitively depend on the neutron richness of reaction system. The structure of evaporation residue excitation function is related to the neutron separation energy and fission barrier of compound nucleus.

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arXiv2021

Production of neutron-rich heavy nuclei around N = 162 in multinucleon transfer reactions

Within the framework of the dinuclear system model, the production mechanism of neutron-rich heavy nuclei around N = 162 has been investigated systematically. The isotopic yields in the multinucleon transfer reaction of $^{238}$U + $^{248}$Cm was analyzed and compared the available experimental data. Systematics on the production of superheavy nuclei via $^{238}$U on $^{252,254}$Cf, $^{254}$Es and $^{257}$Fm is investigated. It is found that the shell effect is of importance in the formation of neutron-rich nuclei around N=162 owing to the enhancement of fission barrier. The fragments in the multinucleon transfer reactions manifest the broad isotopic distribution and are dependent on the beam energy. The polar angles of the fragments tend to the forward emission with increasing the beam energy. The production cross sections of new isotopes are estimated and heavier targets are available for the neutron-rich superheavy nucleus formation. The optimal system and beam energy are proposed for the future experimental measurements.

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arXiv2021

Hyperon dynamics and production of multi-strangeness hypernuclei in heavy-ion collisions at 3A GeV

Within the microscopic transport, systematic investigation of the many facets of hyperons and hypernuclei up to strangeness $S = -2$ are carried out for $^{197}$Au + $^{197}$Au and $^{40}$Ca + $^{40}$Ca at the incident energy of $3A$ GeV. The spatial, temporal and density distributions of hyperon production, absorption and freeze-out are thoroughly investigated. The rapidity and kinetic energy spectra of $Ξ$ hyperons and double $Λ$ hypernuclei are analyzed. It is revealed that the chemical balance of hyperon production is established in baryon-baryon channels while the opposite is found in baryon-meson channels. It turns out that the rapidity spectra of $^{4,5}_{ΛΛ}$X are single-peak and more than two orders of magnitude lower than that of $^{3}_Λ$H. Formation of double $Λ$ hypernuclei through $Ξ$ hypernuclei as intermediate states is also discussed in kinematics.

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arXiv2021

Hyperon Dynamics in Heavy-ion Collisions near threshold energy

Within the framework of quantum molecular dynamics transport model, the isospin and in-medium effects on the hyperon production in the reaction of $^{197}$Au + $^{197}$Au are investigated thoroughly. A repulsive hyperon-nucleon potential from the chiral effective field theory is implemented into the model, which is related to the hyperon momentum and baryon density. The correction on threshold energy of the elementary hyperon cross section is taken into account. It is found that the $Σ$ yields are suppressed in the domain of midrapidity and kinetic energy spectra with the potential. The hyperons are emitted in the reaction plane because of the strangeness exchange reaction and reabsorption process in nuclear medium. The $Σ^{-}/Σ^{+}$ ratio depends on the stiffness of nuclear symmetry energy, in particular in the high-energy region (above 500 MeV).

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arXiv2021

Comparison of Heavy-Ion Transport Simulations: Mean-field Dynamics in a Box

Within the transport model evaluation project (TMEP) of simulations for heavy-ion collisions, the mean-field response is examined here. Specifically, zero-sound propagation is considered for neutron-proton symmetric matter enclosed in a periodic box, at zero temperature and around normal density. The results of several transport codes belonging to two families (BUU-like and QMD-like) are compared among each other and to exact calculations. For BUU-like codes, employing the test particle method, the results depend on the combination of the number of test particles and the spread of the profile functions that weight integration over space. These parameters can be properly adapted to give a good reproduction of the analytical zero-sound features. QMD-like codes, using molecular dynamics methods, are characterized by large damping effects, attributable to the fluctuations inherent in their phase-space representation. Moreover, for a given nuclear effective interaction, they generally lead to slower density oscillations, as compared to BUU-like codes. The latter problem is mitigated in the more recent lattice formulation of some of the QMD codes. The significance of these results for the description of real heavy-ion collisions is discussed.

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arXiv2020

Light fragment and neutron emission in high-energy proton induced spallation reactions

The dynamics of high-energy proton-induced spallation reactions on target nuclides of $^{136}$Xe, $^{59}$Ni, $^{56}$Fe, $^{208}$Pb, $^{184}$W, $^{181}$Ta, $^{197}$Au and $^{112}$Cd, are investigated with the quantum molecular dynamics transport model. The production mechanism of light nuclides and fission fragments is thoroughly analyzed. The statistical code GEMINI is employed in conjunction to the model for managing the decay of primary fragments. For the treatment of cluster emission during the preequilibrium stage, a surface coalescence model is implemented into the model. It is found that the available data of total cross sections are well reproduced with the combined approach for the spallation reactions on both the heavy and light targets, i.e., $^{56}$Fe and $^{208}$Pb, while it is underestimated in the intermediate-mass-fragment region for the medium-mass target $^{136}$Xe. The energetic clusters are mainly contributed from the preequilibrium recognition, in which the quantum tunneling is taken into account. On the other hand, a fairly well overall description of light cluster and neutron emission is obtained and detailed discrepancies with respect to the experimental results are discussed. Possible modifications on the description of spallation reactions are stressed and compared with both recent experimental and theoretical results in the literature.

nucl-th↗

arXiv2020

Strangeness production and hypernuclear formation in proton and antiproton induced reactions

Strange particles and hyperfragments in collisions of antiprotons and protons on nuclei have been investigated systematically within a microscopic transport model. The hyperons are produced from the annihilation in antibaryon-baryon collisions and strangeness exchange process in antiproton induced reactions. A coalescence approach is used for constructing the primary hyperfragments in phase space and the statistical model is modified for describing the decay of hyperfragments via evaporating hyperon, neutron, charged particles etc, in which the shell effect, binding energy and root-mean-square radii are taken into account. It is found that the influence of the hyperon-nucleon interaction on the free $Λ$ and $Ξ^{-}$ production is negligible. However, the large hyperfragment yields are obvious with the attractive potential. The production of double strangeness hyperfragments are reduced below 1$μb$ in comparison to the yields of $Λ$-hyperfragments with the cross sections of 0.05-0.1 mb in the antiproton induced reactions on $^{63}$Cu at the incident momenta of 1-5 GeV/c. The light hyperfragments are formed in the dynamical fragmentation process. The energy dependence of hyperfragment formation is weak once the incident energy above the threshold energy for the hyperon production.

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arXiv2020

Production mechanism of neutron-deficient actinide isotopes in complete fusion reactions and multinucleon transfer reactions

Within the dinuclear system model, unknown neutron-deficient isotopes Np, Pu, Am, Cm, Bk, Cf, Es, Fm are investigated in $^{40}$Ca, $^{36,40}$Ar, $^{32}$S, $^{28}$Si,$^{24}$Mg induced fusion-evaporation reactions and multinucleon transfer reactions with radioactive beams $^{59}$Cu,$^{69}$As,$^{90}$Nb,$^{91}$Tc, $^{94}$Rh, $^{105,110}$Sn, $^{118}$Xe induced with $^{238}$U near Coulomb barrier energies. The production cross sections of compound nuclei in the fusion-evaporation reactions and fragments yields in the multinucleon transfer reactions are calculated within the model. A statistical approach is used to evaluate the survival probability of excited nuclei via the both reaction mechanisms. A dynamical deformation is implemented into the model in the dissipation process. It is found that charge particle channels (alpha and proton) dominate in the decay process of proton-rich nuclides and the fusion-evaporation reactions are favorable to produce the new neutron-deficient actinide isotopes. The total kinetic energies and angular spectra of primary fragments are strongly dependent on colliding orientations.

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arXiv2020

Formation and dynamics of exotic hypernuclei in heavy-ion collisions

The dynamics of exotic hypernuclei in heavy-ion collisions has been investigated thoroughly with a microscopic transport model. All possible channels on hyperon ($Λ$, $Σ$ and $Ξ$) production near threshold energies are implemented in the transport model. The light complex fragments (Z$\leq$2) are constructed with the Wigner-function method. The classical phase-space coalescence is used for recognizing heavy nuclear and hyperfragments and the statistical model is taken for describing the decay process. The nuclear fragmentation reactions of the available experimental data from the ALADIN collaboration are well reproduced by the combined approach. It is found that the in-medium potentials of strange particles influence the strangeness production and fragment formation. The hyperfragments are mainly created in the projectile or target-like rapidity region and the yields are reduced about the 3-order magnitude in comparison to the nuclear fragments. The hypernuclear dynamics of HypHI data is well described with the model. The possible experiments for producing the neutron-rich hyperfragments at the high-intensity heavy-ion accelerator facility (HIAF) are discussed.

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