Directed flow in heavy-ion collisions at NICA: what is interesting to measure?

TL;DR

This paper investigates the directed flow of hadrons in nuclear collisions at NICA energies, highlighting how flow softening and antiflow can occur due to rescattering, and proposes measurements to differentiate between quark-gluon plasma formation and other effects.

Contribution

It introduces specific measurements at NICA to distinguish between flow softening caused by rescattering and signals of quark-gluon plasma formation.

Findings

Proton flow slope tends to zero with increasing impact parameter.

At very peripheral collisions, the flow becomes negative (antiflow).

Rescattering in nuclear remnants causes flow softening.

Abstract

We study the formation of the directed flow of hadrons in nuclear collisions at energies between AGS and SPS in Monte Carlo cascade model. The slope of the proton flow at midrapidity tends to zero (softening) with increasing impact parameter of the collision. For very peripheral topologies this slope becomes negative (antiflow). The effect is caused by rescattering of hadrons in remnants of the colliding nuclei. Since the softening of the proton flow can be misinterpreted as indication of the presence of quark-gluon plasma, we propose several measurements at NICA facility which can help one to distinguish between the cases with and without the plasma formation.