Hydrodynamic simulations of directed flow for light hadrons in Au+Au and isobar collisions $\sqrt{s_{\textrm{NN}}}=$ 200 GeV

TL;DR

This study uses (3+1)-D hydrodynamic simulations to analyze the directed flow of light hadrons in Au+Au and isobar collisions at 200 GeV, revealing system size dependence and insensitivity to nuclear quadrupole deformation.

Contribution

It provides a detailed hydrodynamic analysis of directed flow in different collision systems, highlighting the role of initial tilt and system size effects.

Findings

Counter-clockwise tilt is a key source of directed flow.

Good agreement with experimental data for central and mid-central collisions.

Directed flow shows clear dependence on system size but not on nuclear quadrupole deformation.

Abstract

Using a (3+1)-D hydrodynamic model CLVisc, we study the directed flow ($v_{1}$) of light hadrons produced in Au+Au, Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\textrm{NN}}}=$ 200 GeV. The evolution of tilted energy density, pressure gradient and radial flow along the $x$-direction are systematically investigated. Counter-clockwise tilt of initial fireball is shown to be a vital source of the directed flow for final light hadrons. A good description of directed flow is provided for light hadrons in central and mid-central Au+Au and isobar collisions at RHIC. Our numerical results show a clear system size dependence for light hadron $v_{1}$ across different collision systems. We further study the effect of nuclear structure on the directed flow and find that the $v_{1}$ for light hadrons is insensitive to the nuclei with quadrupole deformation.