# 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!

## Low $p_{T}$ direct photon production from small to large 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 Electromagnetic and weak probes

### Speaker

Wenqing Fan (Stony Brook University)

### Description

Direct photons are unique probes to study both the thermal and collective properties of the Quark Gluon Plasma (QGP). PHENIX has discovered a large excess of the direct photon yield as well as a large azimuthal anisotropy at the low $p_{T}$ region in Au+Au collisions at  $\sqrt{s_{NN}}=200$ GeV$/c^{2}$. The two observations of large yield and anisotropy are quite challenging for the current theoretical models to reconcile simultaneously. To provide more constrains and insights to the theoretical picture, PHENIX is making a more precise measurements for both yield and anisotropy using the high statistics data sample of Au+Au collisions taken in 2014, where photons are reconstructed via conversions to $e^{+}e^{-}$ pairs. As evidence mounts for a collective behavior in small systems, PHENIX also measured the direct photon production in p+Au collisions to see if there is any thermal signal in small systems. In this poster we will present the updated result on direct photon yields and azimuthal anisotropies $v_{2}$ and $v_{3}$ in Au+Au collisions at 200 GeV$/c^{2}$ and the status of direct photon yields in p+Au collisions at the same beam energy.

Collaboration PHENIX Presenter name already specified Experiment

### Primary author

Wenqing Fan (Stony Brook University)