Global and local spin polarization of Λ hyperons in relativistic heavy ion collisions

Abstract

This study presents a novel approach by integrating vorticity, viscosity, and the magnetic field within a unified second order relativistic viscous hydrodynamics framework. Using the developed framework, we estimate the global spin polarization of Λ hyperons by analyzing vorticity evolution at the freeze-out hypersurface. The intricate interplay between vorticity, viscosity, and the magnetic field contributes to the complexity of medium evolution, providing valuable insights into the hyperon polarization in relativistic heavy-ion collisions. Furthermore, we utilize hydrodynamic and transport models to investigate the local spin polarization of Λ hyperons resulting from thermal vorticity and thermal shear in Au+Au and Pb+Pb collisions at sNN = 200 GeV and 5.02 TeV, respectively. © 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.