Strangeness in Quark Matter 2022 (SQM 2022)

Measurements of global and local polarization of hyperons in 200 GeV isobar collisions from STAR

14 Jun 2022, 14:20

20m

GBR1

Talk Bulk matter phenomena, QCD phase diagram, and Critical point PA-Bulk matter phenomena, QCD phase diagram, and Critical point

Speakers

Xingrui Gou (Shandong University) Xingrui Gou

Description

In heavy-ion collisions, the observation of the global and local polarization of hyperons has revealed the existence of large vorticities perpendicular to reaction plane due to systems’s orbital angular momentum and along beam direction due to collective velocity field, respectively. With the high-statistics data from isobar collisions of Ru+Ru and Zr+Zr at $\sqrt{s_{NN}}$ = 200 GeV collected by the STAR experiment, we present differential measurements of global polarization for $\mathrm{\Lambda }/\overline{\mathrm{\Lambda }}$ and ${\mathrm{\Xi }}^{\pm }$ as a function of centrality, $p_T$, and $\eta$. These measurements allow us to study the possible magnetic field driven effects through the polarization difference between Ru+Ru and Zr+Zr, owing to a larger magnetic field in the former. Furthermore, the first measurements of $\mathrm{\Lambda }$ hyperon local polarization along beam direction relative to the third order event plane as well as the second order event plane will be presented. A comparison of results from isobar and Au+Au collisions provides important new insights into the collision system size dependence of the vorticities in heavy-ion collisions.

Presentation materials

SQM2022 talk_Xingrui Gou.pdf