arXiv subjects

Hai-Cheng Wang

Publications and source records attributed to Hai-Cheng Wang.

4 recordsLinked to original sources

arXiv2025

A comparison study of collisions at relativistic energies involving light nuclei

We present extensive comparisons of $^{16}$O+$^{16}$O collisions at the center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=200$ GeV and $^{208}$Pb+$^{16}$O collisions at $\sqrt{s_{NN}}=68.5$ GeV as well as $^{20}$Ne+$^{20}$Ne collisions at $\sqrt{s_{NN}}=200$ GeV and $^{208}$Pb+$^{20}$Ne collisions at $\sqrt{s_{NN}}=68.5$ GeV based on a multiphase transport (AMPT) model. We recommend measuring the ratio of the elliptic flow to the triangular flow, which shows appreciable sensitivity to the structure of light nuclei as also found in other studies. This is especially so if the observable is measured near the target rapidity in $^{208}$Pb+$^{16}$O or $^{208}$Pb+$^{20}$Ne collisions, as originally found in the present study. Our study serves as a useful reference for understanding the structure effect on observables in collisions involving light nuclei under analysis or on the schedule.

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arXiv2025

Disentangling effects of nucleon size and nucleus structure in relativistic heavy-ion collisions

While relativistic heavy-ion collisions become an alternative way of studying nucleus structure, the accurate extraction of nucleus structure could be hampered by the uncertainty of nucleon size, and the latter has attracted people's attention in the past few years. We have compared the impacts of nuclear size and nucleus structure on deformation probes in relativistic heavy-ion collisions based on a multiphase transport (AMPT) model. With increasing nucleon size, the absolute values of the deformation probes are generally reduced due to smeared initial density fluctuations. In heavy systems such as $^{197}$Au+$^{197}$Au collisions, neglecting the nucleon size could underestimate or overestimate significantly the extracted deformation parameter depending on the used deformation probe, while the scaled anisotropic flow and the scaled Pearson correlation coefficient of flow and transverse momentum are good probes of the nucleus deformation rather insensitive to the nucleon size. In small systems such as $^{16}$O+$^{16}$O collisions, the deformation probes are generally more sensitive to the nucleon size than to the nucleus structure, and the transverse momentum fluctuation less sensitive to detailed nucleus structure may serve as a good probe of the nucleon size.

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arXiv2025

Directly probing existence of $α$-cluster structure in $^{20}$Ne by relativistic heavy-ion collisions

Can relativistic heavy-ion collisions only probe the global shape of colliding nuclei, or their detailed internal structure as well? Taking $^{20}$Ne as an example, we attempt to directly probe its internal $α$-cluster structure, by comparing experimentally measured observables in collisions at relativistic energies from density distributions of $^{20}$Ne with and without $α$-cluster structure. Since the two density distributions give the same nucleus size and deformation, they lead to similar mid-rapidity observables. However, the $α$-cluster structure may considerably reduce the free spectator nucleon yield and enhance the spectator light nuclei yield, as a result of more compact initial phase-space distribution of nucleons inside $α$ clusters. We propose to measure the scaled yield ratio of free spectator neutrons to charged particles with mass-to-charge ratio $A/Z = 3$, 3/2, and 2 in ultra-central $^{20}$Ne+$^{20}$Ne collisions, which is found to be reduced by about $25\%$ at $\sqrt{s_\mathrm{NN}} = 7$ TeV and about $20\%$ at $\sqrt{s_\mathrm{NN}} = 200$ GeV with $α$-cluster structure in $^{20}$Ne. This scaled yield ratio thus serves as a robust and direct probe of the existence of $α$-cluster structure in $^{20}$Ne free from the uncertainty of mid-rapidity dynamics.

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arXiv2024

Deformation probes for light nuclei in their collisions at relativistic energies

We have investigated the performance of anisotropic flows $\langle v_n^2 \rangle$, transverse momentum fluctuations $\langle δp_T^2 \rangle $, and their correlations $\langle v_n^2 δp_T \rangle$ in central collisions at relativistic energies as probes of deformation parameters $β_n$ of colliding nuclei, if these nuclei are light nuclei with large $β_n$ and different configurations of $α$ clusters. The effects from higher-order $β_n$ terms are illustrated by derived relations based on the overlap of two nuclei with uniform density distributions and by dynamic simulations of collisions of heavy nuclei whose density distributions are of a deformed Woods-Saxon (WS) form. While the linear relations between $β^2_n$, $\langle v_n^2 \rangle$, and $\langle δp_T^2 \rangle$ and that between $β^3_n$ and $\langle v_n^2 δp_T \rangle$ can be violated for extremely large $β_{n}$, they are mostly valid for realistic values of $β_n$, as long as the density distribution of colliding nuclei can be described by a deformed WS form. However, these linear relations are generally not valid with more realistic density distributions of light nuclei with $α$ clusters, and the amount of deviation depends on the detailed $α$-cluster configurations. Care must be taken when one tries to extract the deformation of light nuclei, and specific probes for $α$-cluster structures in these nuclei are very much needed.

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