Speaker
Description
The properties of the QGP medium produced in relativistic heavy-ion collisions can be explored using the directed flow ($v_{1}$) of the azimuthal angle distribution in momentum space. Hydrodynamic and nuclear transport models indicate that $v_{1}$ in the midrapidity region is sensitive to expanding participant matter during the early collision stages. Spectator nucleons influence the directed flow of identified hadrons, especially when the nuclear passage time is not short compared to the medium expansion time, which is also related to the radii of the colliding nuclei. Thus, studying the system size dependence of $v_{1}$ can provide insights into the QGP properties. This talk will present rapidity-odd directed flow ($v_{1}$) in various collision systems (O+O, Cu+Cu, Ru+Ru, Zr+Zr, Au+Au, U+U) at $\sqrt{s_{NN}} =$ 200 GeV using the AMPT model. We will discuss the slope of directed flow ($dv_{1}/dy$) across different systems.
A non-zero $\Delta v_{1}$ at non-zero $\Delta q$ has been proposed as a violation of the coalescence sum rule and attributed to electromagnetic fields, especially if $\Delta v_{1}$increases with $\Delta q$. Our recent study suggests a coalescence sum rule for the $v_1$ difference ($\Delta v_{1}$) among seven hadron species ($K^{-}$, $\phi, \overline{p}$, $\overline{\Lambda}$, $\overline{\Xi}^{+}$, $\Omega^{-}$ and $\overline{\Omega}^{+}$). We found that $\Delta v_{1}$ depends linearly on both the electric charge difference, $\Delta q$ and strangeness difference, $\Delta S$. This talk will also discuss the results of the coalescence sum rule in the beam energy range of $\sqrt{s_{NN}} =$ 7.7-200 GeV using the AMPT model.
