Speaker
Barbara Trzeciak
(Czech Technical University in Prague)
Description
Despite extensive studies, the J/$\psi$ production mechanism in hadron collisions is not yet exactly known.
For many years, mostly J/$\psi$ differential cross-section measurements have been used to test different J/$\psi$ production models. While many models can reasonably well describe the experimental data on the J/$\psi$ cross-section in $p+p$ collisions, they have different predictions for the J/$\psi$ polarization. Therefore, measurements of the J/$\psi$ polarization may provide further constraints for the models and new insight into the J/$\psi$ production mechanism.
In this presentation, a measurement of J/$\psi$ polarization in $p+p$ collisions at $\sqrt{s}$ = 500 GeV via the dielectron decay channel at mid-rapidity with the STAR experiment will be shown. This measurement has been performed in a wide transverse momentum range of 5 $< p_{T} <$ 16 GeV/$c$. Two polarization parameters $\lambda_{\theta}$ and $\lambda_{\phi}$, related to the polar and azimuthal anisotropy respectively, have been extracted in two reference frames: helicity and Collins-Soper. The frame invariant parameter, $\tilde{\lambda}$, has also been determined as a function of $p_{T}$ in these two frames.
| On behalf of collaboration: | STAR |
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Author
Barbara Trzeciak
(Czech Technical University in Prague)
