Speaker
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.
| Content type | Experiment |
|---|---|
| Collaboration | STAR |
| Centralised submission by Collaboration | Presenter name already specified |
