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Gao-Chan Yong

Publications and source records attributed to Gao-Chan Yong.

At least 37 records · Page 2Linked to original sources
arXiv2022

Effects of high-momentum tail of nucleon momentum distribution on initiation of cluster production in heavy-ion collisions at intermediate energies

Based on the transport model isospin-dependent Boltzmann-Uehling-Uhlenbeck coupled with a phase-space coalescence afterburner, we studied the effects of the high-momentum tail (HMT) of nucleon momentum distribution in initialization in 197Au+197Au reactions at a beam energy of 400 MeV/nucleon with different impact parameters.We found remarkable impact parameter-dependent HMT effects on the fragment multiplicity distribution. The average neutron to proton ratio of produced isotopes is also affected by the HMT. The rapidity distributions of triton and 3He and their elliptic flows are all evidently affected by the HMT. All the effects of the HMT on the cluster production in heavy-ion collisions are centrality dependent.

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arXiv2022

Isospin blocking and its effects in heavy-ion collisions

A concept of \emph{isospin blocking} in the process of isospin diffusion in heavy-ion collisions is raised. Generally, in the process of isospin diffusion, isospin asymmetry would diffuse from the place with large asymmetry to the place with small asymmetry. However, our study shows that the isospin diffusion could be blocked in case the local value of the symmetry energy is larger. We dub this phenomenon ``isospin blocking''. To check this behavior, in the framework of an Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, isospin diffusions in the isotope Sn+Sn reactions at 270 MeV/nucleon are studied. It is shown that the value of the after-diffusion asymmetry is distinctly blocked if the local symmetry energy is large. The effects of the isospin blocking on the isospin asymmetry of dilute and dense matter and the final $π^-/π^+$ ratio in heavy ion collisions are demonstrated.

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arXiv2022

Probing high-density nuclear symmetry energy with $Ξ^{-}/Ξ^{0}$ ratio in heavy-ion collisions at $\sqrt{s_{NN}} \sim 3$ GeV

Recent beam energy scan (BES) experiments at RHIC by the STAR Collaboration (PLB {\bf 827},137003 (2022) and PRL {\bf 128}, 202303 (2022)) found that hadronic interactions dominate the collective flow and the proton cumulant ratios are driven by baryon number conservation in a region of high baryon density in $\sqrt{s_{NN}}$ = 3 GeV Au+Au reactions, indicating the dense medium formed in such collisions is likely hadronic matter. Within an updated ART (A Relativistic Transport) model with momentum dependent isoscalar and isovector single-nucleon mean-field potentials corresponding to different symmetry energies at suprasaturation densities, the $n/p$, $π^{-}/π^{+}$, $K_{s}^{0}/K^{+}$, $Σ^{-}/Σ^{+}$ and $Ξ^{-}/Ξ^{0}$ ratios are studied for central Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV where the maximum central density reaches about $(3.6\sim 4.0)ρ_0$. The doubly strange $Ξ^{-}/Ξ^{0}$ ratio is found to have the strongest sensitivity to the variation of high-density nuclear symmetry energy. Thus, the $Ξ^{-}/Ξ^{0}$ ratio in relativistic heavy-ion reactions at $\sqrt{s_{NN}} \sim 3$ GeV may help probe sensitively the poorly known symmetry energy of dense neutron-rich matter critically important for understanding various properties of neutron stars.

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arXiv2022

Formation of large chunk of nuclear matter in heavy-ion collisions

In terrestrial laboratory with existing accelerators, the maximum multinucleon system produced so far is limited to that with total nucleon number being less than the sum of two colliding nuclei. Such situation may hinder our studies on the properties of nuclear many-body system. Here a way of producing large multinucleon system via multi-nucleus collision device Collider Plus in terrestrial laboratory is proposed. It is shown that large chunk of nucleonic matter can be produced through nuclear ternary fusion reactions at lower beam energies and also large block of dense matter can be formed via ternary collisions of heavy nuclei at intermediate energies. These investigations may shed lights on the studies of the synthesis of superheavy elements and the properties of bulk superdense nuclear matter.

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arXiv2022

Nucleon momentum gap in asymmetric nuclear matter

For more than half a century, nucleons are considered to move continuously in the nuclei. Recent electron-scattering experiments indicate about 20$\sim$25\% nucleons in heavier nuclei are involved in the neutron-proton short-range correlations. Nucleons in the nuclei thus have abnormal behavior unlike those in the non-interaction fermi gas. In the neutron-rich nuclei, around the Fermi momentum, the neutron-proton short-range correlations lead to a momentum gap in the proton momentum distribution, which is circumstantially supported by the pionic experimental data. Likewise, there should also be a neutron momentum gap in the proton-rich nuclei. Nucleon momentum gap is thought to have profound and extensive implications in the studies ranging from particle physics to neutron stars as well as ultra-cold atomic gases.

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arXiv2021

Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay

We study the quiescent luminosities of accreting neutron stars by a new mechanism as neutrino heating for additional deep crustal heating, where the neutrino heating is produced by charged pions decay from the nuclear collisions on the surface of neutron star during its active accretion. For low mass neutron star($\lesssim1.4~M_{\odot}$), as the neutrino heating is little($\lesssim1$ MeV per accreted nucleon) or there would be no neutrino heating, the quiescent luminsoity will be not affected or slightly affected. While for massive neutron star ($\gtrsim2~M_{\odot}$), the quiescent luminosity will be enhanced more obviously with neutrino heating in the range 2-6 MeV per accreted nucleon. The observations on cold neutron stars such as 1H 19605+00, SAX J1808.4-3658 can be explained with neutrino heating if a fast cooling and heavy elements surface are considered. The observations on a hot neutron star such as RX J0812.4-3114 can be explained with neutrino heating if the direct Urca process is forbidden for a massive star with light elements surface, which is different from the previous work that the hot observations should be explained with small mass neutron star and the effect of superfluidity.

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arXiv2021

Imprints of high-momentum nucleons in nuclei on hard photons from heavy-ion collisions around the Fermi Energy

The short-range correlation (SRC) induced by the tensor force in the isosinglet neutron-proton interaction channel leads to a high-momentum tail (HMT) in the single-nucleon momentum distributions n(k) in nuclei. Owing to the remaining uncertainties about the tensor force, the shape of the nucleon HMT may be significantly different from the dilute interacting Fermi gas model prediction $n(k) \sim1/k^4$ similar to the HMT in cold atoms near the unitary limit. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating approximately the nucleon HMT, we investigate hard photon emissions in $^{14}$N+$^{12}$C and $^{48}$Ca+$^{124}$Sn reactions at beam energies around the Fermi energy. Imprints of different shapes of the HMT on the energy spectrum, angular distribution and transverse momentum spectrum of hard photons are studied. While the angular distribution does not carry any information about the shape of the nucleon HMT, the energy spectra and especially the mid-rapidity transverse momentum spectra of hard photons are found to bare strong imprints of the shapes of nucleon HMTs in the two colliding nuclei.

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arXiv2021

Double strangeness $Ξ^{-}$ production as a probe of nuclear equation of state at high densities

Double strangeness $Ξ^{-}$ production in Au+Au collisions at 2, 4, and 6 GeV/nucleon incident beam energies is studied with the pure hadron cascade version of a multi-phase transport model. It is found that due to larger nuclear compression, the model with the soft equation of state (EoS) gives larger yields of both single strangeness ($K^{+}$ and $Λ+Σ^{0}$) and double strangeness $Ξ^{-}$. The sensitivity of the double strangeness $Ξ^{-}$ to the EoS is evidently larger than that of $K^{+}$ or $Λ+Σ^{0}$ since the phase-space distribution of produced $Ξ^{-}$ is more compact compared to those of the single strangeness. The larger sensitivity of the yields ratio of $Ξ^{-}$ to the EoS from heavy and light systems is kept compared to that of the single strangeness. The study of $Ξ^{-}$ production in relativistic heavy-ion collisions provides an alternative for the ongoing heavy-ion collision program at facilities worldwide for identifying the EoS at high densities, which is relevant to the investigation of the phase boundary and onset of deconfinement of dense nuclear matter.

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arXiv2021

Symmetry energy extracted from the S$π$RIT pion data in Sn+Sn systems

With the improved particular Isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model (impIBUU) including the nucleon-nucleon short-range correlations, the ratios and yields of $π^{-}$ and $π^{+}$ in Sn+Sn systems with different asymmetries at 270 MeV/nucleon are studied. It is found that the yields of $π^{-}$ and $π^{+}$ and their ratios in Sn+Sn systems characterized by different neutron to proton ratios obtained from the very recent S$π$RIT pion data, are quite well described by the model, especially when a soft symmetry energy with $L(ρ_{0})$ = 66.75$\pm$24.75 MeV is used. The calculations also clearly demonstrate that the high-momentum tail of the nucleon initialization in momentum space strongly affects the yields and ratios of pion production in Sn+Sn systems with different asymmetries near or below threshold. In addition, given many insoluble theoretical uncertainties in transport models, multi-system experimental measurements with various N/Z asymmetries are proposed to extract the symmetry energy less model-dependently by using heavy-ion collisions.

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arXiv2021

Probing the boundary of phase transition of nuclear matter using proton flows in heavy-ion collisions at 2-8 GeV/nucleon

Based on the relativistic transport model ART with the hadronic equation of state extended to have a phase transition via the use of the MIT bag model, properties of phase transition of dense nuclear matter formed in relativistic heavy-ion collisions are investigated. Proton sideward and directed flows are calculated with different equation of states in Au + Au collisions at beam energies of 2, 4, 6 and 8 GeV/nucleon. Compared with AGS experimental data in existence, the boundary of first-order phase transition is roughly confined, i.e., in the range of 2.5-4 times saturation density with temperature about 64-94 MeV. Such constraints are useful for ongoing RHIC Beam Energy Scan-II program to study the QCD matter phase diagram.

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arXiv2021

Probing in-medium nucleon-nucleon inelastic scattering cross section by using energetic n/p ratio

Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the in-medium nucleon-nucleon inelastic scattering ( which is dominated by pion production at low and intermediate energies) is explored. It is found that the in-medium modification of nucleon-nucleon inelastic scatterings appears to reduce the neutron to proton ratio n/p at higher kinetic energies. Although the in-medium modification of nucleon-nucleon inelastic scatterings, as expected, affects the value of $π^-/π^+$ ratio, considering a series of undetermined properties of delta resonance and $π$ in medium, the energetic neutron to proton ratio n/p is more suitable to be used to probe the in-medium correction of nucleon-nucleon inelastic scatterings.

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arXiv2020

Pion production and absorption in heavy-ion collisions

Based on the isospin dependent transport model IBUU, the pion production and its absorption are thoroughly studied in the central collision of $Au+Au$ at a beam energy of 400 MeV/nucleon. It is found that the pions are firstly produced by the hard $Δ$ decay at the average density around $1.75ρ_{0}$, whereas about 18\% of them are absorbed absolutely in the subsequent inelastic collisions. For the free pions observed, more than half of them have been scattered for one or more times before they are free from matter. And the more scattering numbers of pions, the higher the momentum they possess. These pions, due to longer time of their existence in high density nuclear matter, carry more information about the symmetry energy of the nuclear matter at high densities.

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arXiv2020

Probing high-density symmetry energy using heavy-ion collisions at intermediate energies

The nuclear symmetry energy, which describes the energy difference of per proton and neutron in nuclear matter, has been extensively studied within the last two decades. Around saturation density, both the value and the slope of the nuclear symmetry energy have been roughly constrained, its high-density behavior is now still in argument. Probing high-density symmetry energy at terrestrial laboratories is being carried out at facilities that offer radioactive beams worldwide. While relevant experiments are being conducted, we theoretically developed more advanced isospin-dependent transport model including new physics such as nucleon-nucleon short-range correlations and in-medium isospin-dependence of baryon-baryon scattering cross section. New sensitive probes of high-density symmetry energy are provided, such as squeezed-out neutron to proton ratio, photon and light cluster as well as the production of mesons with strangeness or hidden strangeness. The blind spots of probing the high-density symmetry energy by sensitive observable are demonstrated. Model dependence of frequently used sensitive probes of the symmetry energy has been studied thoroughly based on different transport models. A qualitative observable of neutron to proton ratio at high emitting energy is proposed to probe the high-density symmetry energy qualitatively. The probed density regions of the symmetry energy are carefully studied. Effects of nucleon-nucleon short-range correlations on the some sensitive observables of the symmetry energy in heavy-ion collisions are explored carefully. Probing the curvature of the symmetry energy by involving the slope information of the symmetry energy at saturation point in the transport model is proposed.

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arXiv2019

Effects of curvature of the symmetry energy in Sn+Sn reactions at 270 MeV/nucleon

Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the isotope Sn+Sn reactions at 270 MeV/nucleon are investigated. It is shown that nucleon and meson observables in the Sn+Sn reactions at 270 MeV/nucleon cannot effectively probe the high-density symmetry energy. These observables, however, are sensitive to the curvature of the symmetry energy. It thus sheds light on the study of the high-density behavior of the nuclear symmetry energy by extracting the curvature of the symmetry energy through the interpretation of forthcoming RIBF/RIKEN related data.

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arXiv2019

High $p_{t}$ squeezed-out n/p ratio as a probe of $K_{\rm{sym}}$ of the symmetry energy

By involving the constraints of the slope of nuclear symmetry energy $L$ into the question of determination of the high-density symmetry energy, one needs to probe the curvature of nuclear symmetry energy $K_{\rm{sym}}$. Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, effects of the curvature of nuclear symmetry energy on the squeezed-out nucleons are demonstrated in the semi-central Au+Au reaction at 400 and 600 MeV/nucleon. It is shown that the squeezed-out isospin-dependent nucleon emissions at high transverse momenta are sensitive to the curvature of nuclear symmetry energy. The curvature of nuclear symmetry energy at saturation density thus can be determined by the high momentum squeezed-out isospin-dependent nucleon emissions experiments from the semi-central Au+Au reaction at 400 or 600 MeV/nucleon.

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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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arXiv2018

Blind spots of probing the high-density symmetry energy in heavy-ion collisions

The nuclear symmetry energy, especially at suprasaturation densities, plays crucial roles in many astrophysical studies. However, nowadays the high-density behavior of the symmetry energy is still very controversial in nuclear community. To constrain the high-density behavior of the symmetry energy, neutron-rich nuclei collisions at medium energies are considered to be one of the most effective methods. While probing the high-density symmetry energy by using heavy-ion collisions, blind spots may exist. In the framework of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the blind spots of probing the high-density symmetry energy by the n/p ratio in the central Au+Au reaction at 300 MeV/nucleon are demonstrated. It is found that the nucleon observable neutron to proton ratio n/p in heavy-ion collisions cannot effectively probe the high-density symmetry energy when the high-density symmetry energy is less density-dependent.

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