# 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!

## Measurement of J/psi Polarization in p+p Collisions at √s = 200 GeV through the Di-muon Channel at STAR

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

Poster Quarkonia

### Speaker

Zhen Liu (University of Science and Technology of China and Brookhaven National Laboratory)

### Description

Quarkonium production mechanism in elementary collisions has not been fully understood. Experimental data on the $J/\psi$ cross section in p+p collisions can be described relatively well by several models that are currently available on the market. However, these models differ in their predictions for the $J/\psi$ polarization. Therefore precise measurements of $J/\psi$ polarization can provide further constraints on the production models. During the RHIC 2015 run, the STAR experiment recorded a large sample of p+p collisions at $\sqrt{s}$ = 200 GeV triggered by the Muon Telescope Detector for charmonium studies via the di-muon decay channel. In this poster, we will present the $J/\psi$ polarization measurement in the helicity and Collins-Soper reference frames utilizing this data set. The polarization parameters $\lambda_{\theta}$ and $\lambda_{\phi}$ are extracted from simultaneous fit to 1-dimensional polar and azimuthal angular distributions of decay $\mu^{+}$ in the J/$\psi$ transverse momentum range of 0-6 GeV/c in both frames. The results will be compared with similar measurements in higher transverse momentum region as well as with model calculations.

Centralised submission by Collaboration Presenter name already specified Experiment STAR

### Primary author

Zhenyu Ye (University of Illinois at Chicago)