Collective Flow of Protons and Negative Pions in Nucleus-Nucleus Collisions at Momentum of $4.2 \div 4.5$ AGeV/c

TL;DR

This study investigates the collective flow of protons and negative pions in nucleus-nucleus collisions at 4.2 to 4.5 AGeV/c, revealing how flow patterns depend on system size and are modeled by the Quark-Gluon String Model.

Contribution

It provides detailed experimental data on flow patterns across different projectile-target combinations and compares these with theoretical model predictions.

Findings

Proton directed flow increases with system mass.

Negative pions flow in the same or opposite direction depending on system size.

Quark-Gluon String Model successfully reproduces flow trends.

Abstract

Collective flow of protons and negative pions has been studied within the momentum region of $4.2 \div 4.5$ AGeV/c ($E =3.4 \div 3.7$ AGeV) for different projectile-target combinations involving carbon and, specifically, He-C, C-C, C-Ne, C-Cu and C-Ta. The data stem from the SKM-200-GIBS streamer chamber and from Propane Bubble Chamber systems utilized at JINR. The directed flow of protons grows dramatically in the carbon region when the counterpart nucleus grows in mass between He and Ta. The elliptic proton flow points out of the reaction plane and also strengthens as system mass increases. Within the reaction plane, the negative pions flow in the same direction as protons for the lighter of the investigated systems, He-C, C-C and C-Ne, and in the opposite direction for the heavier, C-Cu and C-Ta. The Quark-Gluon String Model reproduces observed changes in the flow with system mass.