Speaker
Description
As recently observed by the STAR and ALICE collaborations, the global and local
spin polarization of $\Lambda$-hyperons provides new insights into spin dynamics
in heavy-ion collisions. There are various contributing factors that could be the
source of hyperon polarization. However, among them, the vorticity field is widely
considered as the primary source of particle polarization in heavy-ion collisions.
Recent findings suggest that the transverse component of the vorticity field drives
global spin polarization, while the longitudinal component accounts for local
polarization. For the first time, within the framework of second-order relativistic
viscous hydrodynamics, we incorporate vorticity, viscosity, and magnetic field
effects into a unified hydrodynamic model to estimate the global polarization of
$\Lambda$-hyperons, using vorticity evolution data at the freeze-out hypersurface.
Additionally, to further elucidate spin-polarization dynamics, we explore the local
polarization of $\Lambda$-hyperons due to thermal vorticity and the thermal shear
tensor in Au+Au and Pb+Pb collisions at $\sqrt{s_{NN}} = 200$ GeV and 5.02
TeV, respectively, by employing hydrodynamic and transport models. As the
coupling between vorticity, viscosity, and magnetic field makes medium evolution
highly complex, our findings provide a unique insight into understanding the
hyperon polarization in relativistic heavy-ion collisions
