PHENIX results on collectivity in small systems

TL;DR

This paper reports measurements of elliptic and triangular flow in small collision systems at RHIC energies, showing hydrodynamical models with quark-gluon plasma formation best explain the observed collectivity.

Contribution

First comprehensive flow measurements in small systems at RHIC energies, comparing data with various models to understand the origin of collectivity.

Findings

Hydrodynamical models best describe the data.

Evidence of collective behavior in small systems.

Supports quark-gluon plasma formation in small collision systems.

Abstract

PHENIX has measured elliptic and triangular flow of charged hadrons in $p/d/^{3}$He$+$Au collisions at a center-of-mass energy of 200 GeV per nucleon pair, and elliptic flow in $d$+Au collisions at 200, 62.4, and 39 GeV. In order to asses the origin of collectivity in the smallest systems, these results are compared with several theoretical models that produce azimuthal particle correlations based on initial and/or final state effects. Hydrodynamical models, which include the formation of a droplet of quark-gluon plasma, provide the best simultaneous description of our observations.