Λ spin polarization in event-by-event relativistic heavy-ion collisions

Abstract

We present a systematic study of Λ hyperon's polarization observables using event-by-event (3+1) dimensional relativistic hydrodynamics. The effects of initial hot spot size and quark gluon plasma's specific shear viscosity on the polarization observables are quantified. We examine the effects of the two formulations of the thermal shear tensor on the polarization observables using the same hydrodynamic background. With event-by-event simulations, we make predictions for the Fourier coefficients of Λ′s longitudinal polarization Pz with respect to the event planes of different orders of anisotropic flow. We propose new correlations among the Fourier coefficients of Pz and charged hadron anisotropic flow coefficients to further test the mapping from fluid velocity gradients to hyperon's polarization. Finally, we present a system size scan with Au+Au, Ru+Ru, and O+O collisions at sNN=200GeV to study the system size dependence of polarization observables at the BNL Relativistic Heavy-ion Collider.