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\textbf{\Large Probing the QCD Phase Structure with Elliptic Flow in Au+Au Collisions at $\sqrt{s_{NN}}$ = 3.0-19.6 GeV at RHIC}\\
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\textbf{Guoping Wang}\\

\textbf{(for the STAR Collaboration)}\\
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In heavy-ion collisions, the elliptic flow ($v_{2}$) represents the second harmonic coefficient in the Fourier expansion of the azimuthal distribution relative to the reaction plane. It serves as a sensitive indicator of the interaction strength among the system’s constituents and offers a valuable means to explore its degrees of freedom.


In this poster, we will present $v_{2}$ measurements for a variety of hadrons, including $\pi^{\pm}$, $K^{\pm}$, $p$, $\overline{p}$, $K^{0}_{S}$, $\phi$, $\Lambda$, $\overline{\Lambda}$, $\Xi^{\pm}$ and $\Omega^{\pm}$ in Au + Au collisions, based on high-statistics datasets from the second phase of the RHIC Beam Energy Scan (BES-II) program measured by STAR. The scaling of $v_{2}$ according to the Number of Constituent Quarks (NCQ) for both particles and antiparticles will be examined. In addition, the NCQ-scaled $v_{2}$ ratios of particles such as $\pi^{+}$/$K^{+}$, $p$/$K^{+}$, $\pi^{-}$/$K^{-}$, $\overline{p}$/$K^{-}$, $\phi$/$K^{-}$, $\Lambda$/$K^{0}_{S}$ and $\overline{\Lambda}$/$K^{0}_{S}$, across the energy range $\sqrt{s_{NN}}$ = 3.0-19.6 GeV will be presented. The inferred information related to the QCD phase structure will be discussed.

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