# Quark Matter 2018

13-19 May 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

## STAR Measurements of Elliptic Flow in Small Collision Systems

15 May 2018, 17:00
2h 40m
First floor and third floor (Palazzo del Casinò)

### First floor and third floor

#### Palazzo del Casinò

Poster Collectivity in small systems

### Speaker

Ms Maria Sergeeva (UCLA)

### Description

The coefficient of the second harmonic in azimuthal anisotropy ($v_2$) of produced particles gives insight to bulk properties of the medium being created in high-energy heavy-ion collisions. These measurements have provided important evidence of the partonic collective motion in the quark-gluon plasma (QGP). In recent years, the study of collective motion in small systems has gained increased attention. These studies aim to answer the questions of how small a QGP droplet can be and what is the boundary between a confined and deconfined medium. However, non-flow correlations, especially due to jets and di-jets, can influence the observed flow and may tend to dominate in small systems. Therefore, special care has to be taken to differentiate collectivity from non-flow contributions.

In this poster, we present the STAR measurements of charged-hadron elliptic flow, $v_2$, in p+Au collisions at $\sqrt{s_{NN}} = 200$ GeV, and in d+Au collisions at 200, 62.4, 39 and 19.6 GeV. Data analysis is done with the event plane method, and with 2-particle and 4-particle cumulants. The results will be shown as a function of multiplicity which provides control of the system size. This will be compared with peripheral Au+Au collisions with similar multiplicities at the same center of mass energies to determine whether or where the onset of the QGP exists in these small systems.

Content type Experiment STAR Presenter name already specified

### Primary author

Zhenyu Ye (University of Illinois at Chicago)

### Presentation Materials

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