Directed flow of charged particles within idealized viscous hydrodynamics at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

TL;DR

This paper introduces a new initial condition model for viscous hydrodynamics in heavy-ion collisions, successfully reproducing directed flow data across RHIC and LHC energies, and constraining initial state asymmetries.

Contribution

It presents an alternative longitudinal tilted initial condition based on Glauber geometry combined with ideal hydrodynamics, improving the understanding of directed flow in heavy-ion collisions.

Findings

The model reproduces directed flow $v_{1}( ext{eta})$ across a wide rapidity range.

Directed flow measurements constrain initial state asymmetries.

The approach works for energies from RHIC to LHC.

Abstract

Following the Boz$\dot{\textrm{e}}$k-Wyskiel parametrization tilted initial condition, an alternative way to construct a longitudinal tilted fireball based on the Glauber collision geometry is presented. This longitudinal tilted initial condition combined with the Ideal-CLVisc (3 + 1)D hydrodynamic model, a nonvanishing directed flow coefficient $v_{1}$ in a wide rapidity range is observed. After comparing the model's results with experimentally observed data of directed flow coefficient $v_{1}(\eta)$ from $\sqrt{s_{NN}}$ = 200 GeV Cu + Cu, Au + Au collisions at RHIC energy to $\sqrt{s_{NN}}$ = 2.76 TeV and $\sqrt{s_{NN}}$ = 5.02 TeV Pb + Pb collisions at the LHC energy. We find that the directed flow measurements in heavy-ion collisions can set strong constraints on the imbalance of forward and backward incoming nuclei and on the magnitude asymmetry of pressure gradients along the $x$ direction.