# Collectivity in small systems measured with PHENIX at RHIC

## TL;DR

This paper demonstrates that azimuthal particle correlations in small collision systems at RHIC are linked to initial geometry and are well described by hydrodynamical models including QGP formation.

## Contribution

It provides the first definitive evidence linking flow coefficients to initial geometry in small systems and validates hydrodynamical models for these conditions.

## Key findings

- $v_2$ and $v_3$ are correlated to initial geometry.
- Hydrodynamical models with QGP describe flow data.
- Flow signals are present in small systems.

## Abstract

In this paper we show azimuthal particle correlations in three different small-system collisions with different intrinsic initial geometries. The simultaneous constraints of $v_2$ and $v_3$ in $p/d/^3$He$+$Au collisions definitively demonstrate that the $v_n$'s are correlated to the initial geometry. In addition, we find that hydrodynamical models which include QGP formation describe simultaneouly the elliptic and triangular flow data in a statistically acceptable manner in all three systems.