# Three Particle Correlations from STAR

## TL;DR

This paper investigates three-particle azimuthal correlations in high-energy collisions to distinguish between different mechanisms of conical emission, such as Mach cones and Cerenkov radiation, by analyzing STAR data across various collision systems.

## Contribution

It provides the first detailed analysis of three-particle correlations to differentiate conical emission scenarios in heavy-ion collisions.

## Key findings

- Results suggest possible evidence for conical flow in Au+Au collisions.
- Background subtraction and flow harmonic uncertainties are thoroughly addressed.
- Data across different collision systems help distinguish emission mechanisms.

## Abstract

Two-particle correlations have shown modification to the away-side shape in central Au+Au collisions relative to $pp$, d+Au and peripheral Au+Au collisions. Different scenarios can explain this modification including: large angle gluon radiation, jets deflected by transverse flow, path length dependent energy loss, Cerenkov gluon radiation of fast moving particles, and conical flow generated by hydrodynamic Mach-cone shock-waves. Three-particle correlations have the power to distinguish the scenarios with conical emission, conical flow and Cerenkov radiation, from other scenarios. In addition, the dependence of the observed shapes on the $p_T$ of the associated particles can be used to distinguish conical emission from a sonic boom (Mach-cone) and from QCD-Cerenkov radiation. We present results from STAR on 3-particle azimuthal correlations for a high $p_T$ trigger particle with two softer particles. Results are shown for $pp$, d+Au and high statistics Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. An important aspect of the analysis is the subtraction of combinatorial backgrounds. Systematic uncertainties due to this subtraction and the flow harmonics v2 and v4 are investigated in detail. The implications of the results for the presence or absence of conical flow from Mach-cones are discussed.