Equation of state dependence of directed flow in a microscopic transport model

Yasushi Nara,Harri Niemi,Jan Steinheimer,Horst Stöcker

doi:10.1016/j.physletb.2017.02.020

Abstract

We study the sensitivities of the directed flow in Au+Au collisions on the equation of state (EoS), employing the transport theoretical model JAM. The EoS is modified by introducing a new collision term in order to control the pressure of a system by appropriately selecting an azimuthal angle in two-body collisions according to a given EoS. It is shown that this approach is an efficient method to modify the EoS in a transport model. The beam energy dependence of the directed flow of protons is examined with two different EoS, a first-order phase transition and crossover. It is found that our approach yields quite similar results as hydrodynamical predictions on the beam energy dependence of the directed flow; Transport theory predicts a minimum in the excitation function of the slope of proton directed flow and does indeed yield negative directed flow, if the EoS with a first-order phase transition is employed. Our result strongly suggests that the highest sensitivity for the critical point can be seen in the beam energy range of 4.7≤sNN≤11.5 GeV.

Highlights

One of the most challenging problems in high energy heavy ion collisions is to map out the QCD phase diagram from low to high baryon densities
It is found that our approach yields quite similar results as hydrodynamical predictions on the beam energy dependence of the directed flow; Transport theory predicts a minimum in the excitation function of the slope of proton directed flow and does yield negative directed flow, if the equation of state (EoS) with a first-order phase transition is employed
At higher beam energies, the microscopic transport models RQMD [24], UrQMD [25], and PHSD/HSD [21] show a negative slope of proton directed flow without a phase transition

Summary

Introduction

One of the most challenging problems in high energy heavy ion collisions is to map out the QCD phase diagram from low to high baryon densities. We study the sensitivities of the directed flow in Au+Au collisions on the equation of state (EoS), employing the transport theoretical model JAM.

Results

Conclusion