# Quark Matter 2017

5-11 February 2017
Hyatt Regency Chicago
America/Chicago timezone

## Measurement of $J/\psi$ azimuthal anisotropy in U+U collisions at $\sqrt{s_{\rm NN}} =193$ GeV by the STAR experiment

Not scheduled
2h 30m
Hyatt Regency Chicago

#### Hyatt Regency Chicago

151 East Wacker Drive Chicago, Illinois, USA, 60601
Board: A21
Poster

### Speaker

Alena Harlenderová (STAR)

### Description

The existence of Quark-Gluon Plasma (QGP) is predicted by lattice QCD at high
temperatures or large nuclear densities.
Various probes were proposed to study this phase of matter, among which $J/\psi$ suppression due to color screening of the quark potential in the QGP is of special interest
since this mechanism implies the formation of the defined matter.
However, contribution from the recombination of charm and anti-charm
quarks in the medium complicates the interpretation of the observed
modification to the $J/\psi$ production in heavy-ion collisions.
Measurements of the second-order harmonic coefficient ($v_2$) of $J/\psi$
azimuthal anisotropy can help disentangle different contributions. For
primordial $J/\psi$ produced at the beginning of the collisions in hard
scatterings, $v_2$ is expected to be close to zero, whereas regenerated
$J/\psi$ should inherit the anisotropy of the constituent charm quarks.

$J/\psi$ $v_2$ has been measured by the STAR experiment to be consistent
with zero for $J/\psi$ $p_{T}>2$ GeV/c in Au+Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV. Since U+U collisions
are expected to create medium of higher energy density compared to Au+Au
collisions, the relative contribution of primordial and regenerated
$J/\psi$ could be different. Therefore, U+U collisions provide a unique
opportunity to test the current understanding of $J/\psi$ production
mechanisms. First results on $J/\psi$ $v_2$ measured via the di-electron
channel in U+U collisions at $\sqrt{s_{\rm NN}} = 193$ GeV will be presented in this
poster, and the implications on the $J/\psi$ production mechanism will be
discussed.

Collaboration STAR Quarkonia