Directed flow in ultrarelativistic heavy-ion collisions

TL;DR

This paper models the generation of directed flow in ultrarelativistic heavy-ion collisions using hydrodynamics, successfully reproducing experimental observations and scaling behaviors across different collision systems.

Contribution

It introduces a hydrodynamic model that explains the negative directed flow by assuming a tilted source, aligning with experimental data and system size scaling.

Findings

Reproduces negative directed flow in experiments.

Shows tilt of the source explains flow patterns.

Matches scaling from Au-Au to Cu-Cu collisions.

Abstract

We study the generation of directed flow in the hydrodynamic expansion of the hot matter formed in ultrarelativistic heavy-ion collisions at 200GeV. The experimentally observed negative directed flow in a wide range of central pseudorapidities isreproduced assuming that the fireball is tilted away from the collision axis. The tilt of the source is consistent with a preferential emission in the forward/backward hemisphere from forward/backward participating nucleons. The model reproduces the experimentally observed scaling of the directed flow when going from Au-Au to Cu-Cu systems.