Speaker
Description
$J/\psi$ serves as an important probe to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. In Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV, it has been observed that the $J/\psi$ yield is strongly suppressed and its elliptic flow ($v_{2}$) is consistent with zero, indicating $J/\psi$'s strong coupling with the medium and its potentially small regeneration contribution. Besides those measurements, the $J/\psi$ polarization can shed new light on the QGP properties and the $J/\psi$ production mechanism in heavy-ion collisions. For example, it has been hypothesized that $J/\psi$ can be polarized due to the spin-orbit coupling between $J/\psi$ and QGP's large angular momentum in non-central heavy-ion collisions. The early production of $J/\psi$ also makes its polarization potentially sensitive to the strong magnetic field at the early stage.
In this poster, we will present the first measurement of $J/\psi$ polarization in heavy-ion collisions at RHIC. The $J/\psi$ polarization in the Helicity frame and Collins-Soper frame, as well as with respect to the event-plane, in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV will be presented, and its physics implications will be discussed.
| Category | Experiment |
|---|---|
| Collaboration (if applicable) | The STAR Collaboration |
