Zhang-Zhu Han | Searcharxiv

arXiv2019

Investigating different $Λ$ and $\barΛ$ polarizations in relativistic heavy-ion collisions

Based on the chiral kinetic equations of motion, spin polarizations of various quarks, due to the magnetic field induced by spectator protons as well as the quark-antiquark vector interaction, are studied within a partonic transport approach. Although the magnetic field in QGP enhances the splitting of the spin polarizations of partons compared to the results under the magnetic field in vacuum, the spin polarizations of $s$ and $\bar s$ quarks are also sensitive to the quark-antiquark vector interaction, challenging that the different $Λ$ and $\bar Λ$ spin polarization is a good measure of the magnetic field in relativistic heavy-ion collisions. It is also found that there is no way to obtain the large splitting of the spin polarization between $Λ$ and $\bar Λ$ at $\sqrt{s_{NN}}=7.7$ GeV with partonic dynamics.

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arXiv2019

Charge asymmetry dependence of the elliptic flow splitting in relativistic heavy-ion collisions

The elliptic flow splitting $Δv_2$ between $\bar{u}$ and $u$ quarks as well as between $π^-$ and $π^+$ in midcentral Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV has been studied, based on the framework of an extended multiphase transport model with the partonic evolution described by the chiral kinetic equations of motion. Within the available statistics, the slope of $Δv_2$ between $\bar{u}$ and $u$ quarks with respect to the electric charge asymmetry $A_{ch}$ from the linear fit is found to be negative, due to the correlation between the velocity and the coordinate in the initial parton phase-space distribution. Simulations with the magnetic field in QGP overestimate the splitting of the spin polarization between $Λ$ and $\barΛ$ observed experimentally, with the latter more consistent with results under the magnetic field in vacuum. Considering the uncertainties from the magnetic field, the quark-antiquark vector interaction, and the hadronization, as well as the hadronic evolution, our study shows that the experimentally observed positive slope of $Δv_2$ with respect to $A_{ch}$ is not likely due to the chiral magnetic wave.

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