Hyperon ($\Lambda$) polarization along the beam axis in Pb-Pb collisions at $\sqrt{𝑠_{\rm{NN}}}=5.36$ TeV with ALICE

by Junlee Kim (Fudan University (CN))

Tuesday 20 Oct 2026, 11:00 → 12:00 Europe/Zurich

500/1-001 - Main Auditorium (CERN)

The quark–gluon plasma (QGP) created in relativistic heavy-ion collisions exhibits collective behaviour resembling that of a nearly perfect fluid.

The anisotropic expansion of this medium generates non-uniform velocity gradients and local vortical structures, which can lead to spin polarization of produced particles. The polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons along the beam axis provides a sensitive probe of these structures and their connection to the collective dynamics of the QGP.

In this seminar, new measurements of longitudinal $\Lambda$ and $\overline{\Lambda}$ polarization in Pb–Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.36$ TeV with the ALICE detector will be presented. The large Run 3 data sample enables a substantially more precise measurement of the polarization relative to the second-order event plane and, for the first time at the LHC, a measurement relative to the third-order event plane.

The results are compared with viscous hydrodynamic calculations, which indicate that the second-order polarization is sensitive to the implementation of QGP bulk viscosity. The third-order measurement provides complementary information on fluctuation-driven vortical structures associated with the initial state. Together, these measurements offer new opportunities to investigate the interplay between local vorticity, spin polarization and the transport properties of the QGP.

 

Coffee will be served at 10h30

 

CERNEP2026_junleekim_v4.pdf

Recording