Flow in small systems in the EPOS4 approach for high-energy scatterings

TL;DR

This paper discusses the EPOS4 model's application to small systems in high-energy collisions, focusing on multiplicity dependence of flow observables to understand collectivity, without specific tuning for flow results.

Contribution

It introduces the application of the EPOS4 model to small systems, analyzing flow and collectivity in high-energy collisions with a general-purpose approach.

Findings

Flow harmonics depend on multiplicity in small systems.

EPOS4 reproduces qualitative features of collectivity.

Model provides insights into particle correlations in small systems.

Abstract

EPOS4 is based on a sophisticated (recently significantly improved) parallel-primary-scattering scenario followed by a hydrodynamic expansion, for all collision systems, from small ones such as proton-proton ($pp$) to big ones such as lead-lead (PbPb). Having already reported on identified particle spectra in recent publications (providing information about radial flow), I discuss here the multiplicity dependence of multi-particle cumulants and flow harmonics, to better understand collectivity in small systems. The model is not particularly tuned for flow results, but it is a "general purpose" approach, trying to accommodate various types of observables with the same model.