Directed and Elliptic Flow

TL;DR

This paper compares microscopic transport model calculations with experimental data on directed and elliptic flow in heavy-ion collisions across a range of energies, revealing consistent descriptions of flow transitions and flow patterns.

Contribution

It demonstrates that transport models with specific mean field potentials can accurately reproduce flow phenomena in heavy-ion collisions at different energies.

Findings

Transition from squeeze-out to in-plane emission in Au+Au collisions

Elliptic flow shows in-plane emission for Pb collisions at SPS energies

Protons and pions exhibit opposite directed flow, with strong flow signals observed

Abstract

We compare microscopic transport model calculations to recent data on the directed and elliptic flow of various hadrons in 2 - 10 A GeV Au+Au and Pb (158 A GeV) Pb collisions. For the Au+Au excitation function a transition from the squeeze-out to an in-plane enhanced emission is consistently described with mean field potentials corresponding to one incompressibility. For the Pb (158 A GeV) Pb system the elliptic flow prefers in-plane emission both for protons and pions, the directed flow of protons is opposite to that of the pions, which exhibit anti-flow. Strong directed transverse flow is present for protons and Lambdas in Au (6 A GeV) Au collisions as well. Both for the SPS and the AGS energies the agreement between data and calculations is remarkable.