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S. S. Shi

Publications and source records attributed to S. S. Shi.

3 recordsLinked to original sources

Light and hyper nuclei formation at $\sqrt{s_{\text{NN}}} =$ 3 GeV Au+Au collisions using Wigner coalescence approach

The production of light nuclei and hyper-nuclei in heavy-ion collisions, particularly at high baryon density, is crucial for understanding the dynamical evolution of the collision system and exploring the internal state of nuclear matter of compacted stellar object. Despite being a topic of ongoing debate, an improved theoretical understanding is necessary. In this work, production of light nuclei ($d$, $t$, $^{3}$He, $^{4}$He) and hyper-nuclei ($^{3}_Λ$H, $^{4}_Λ$H) was investigated using the JAM microscopic transport model combined with an afterburner coalescence process at $\sqrt{s_{\text{NN}}} =$ 3 GeV Au+Au collisions. The formation of a specific nucleus during the coalescence process is determined by its Wigner function. The comparison of the calculations for $\mathrm{p_T}$ spectra, average $\mathrm{p_T}$, and rapidity distributions to the measurements from the STAR experiment was performed. We investigated the dynamic information carried by light nuclei and determined the averaged spatial distance $\langle ΔR \rangle$ and momentum difference $\langle ΔP \rangle$ of constituent nucleons ($Λ$) for each nucleus species.

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Improvement of heavy flavor productions in a multi-phase transport model updated with modern nPDFs

Recently we have updated a multi-phase transport (AMPT) model with modern parton distribution functions of nuclei (nPDFs). Here we study open charm production in the updated AMPT model and compare to the experimental data from $pp$ and $AA$ collisions over a wide range of collision energies. Besides the update of nPDFs, we have removed the transverse momentum cutoff on initial heavy quark productions and also included the resultant heavy flavor cross section into the total minijet cross section in the initial condition as described by the HIJING model. We show that the AMPT model with these updates provides a much better description of the yields and transverse momentum spectra of various open charm hadrons in comparison with the experimental data. This lays the foundation for further heavy flavor studies within the transport model approach.

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Higher Moments of Net-Baryon Distribution as Probes of QCD Critical Point

It is crucially important to find an observable which is independent on the acceptance and late collision process, in order to search for the possible Critical Point predicted by QCD. By utilizing A Multi-Phase Transport (AMPT) model and Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model, we study the centrality and evolution time dependence of higher moments of net-baryon distribution in Au + Au collisions at $\sqrt{s_{NN}}=17.3$ GeV. The results suggest that Kurtosis and Skewness are less sensitive to the acceptance effect and late collision process. Thus, they should be good observables providing the information of the early stage of heavy ion collision. In addition, our study shows that the Kurtosis times $σ^{2}$ of net-proton distribution are quite different to that of net-baryon when collisions energy is lower than $\sqrt{s_{NN}}$ = 20 GeV, the Monte Calor calculations on Kurtosis$\cdotσ^{2}$ have a deviation from the theoretical predictions.

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