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

TL;DR

This study investigates how the directed flow in gold-gold collisions depends on the equation of state using a modified transport model, revealing sensitivity to phase transition signals and potential critical point indicators.

Contribution

The paper introduces a novel collision term modification in a transport model to control the EoS, enabling detailed study of directed flow sensitivity to phase transitions.

Findings

Transport model reproduces hydrodynamical predictions for directed flow.

Negative directed flow observed with first-order phase transition EoS.

Maximum sensitivity to the critical point in the beam energy range 4.7-11.5 GeV.

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 $4.7\leq\srtNN\leq11.5$ GeV.