Experimental Studies of Global Polarization in Heavy-ion Collisions

The huge orbital angular momentum generated by non-central relativistic heavy-ion collisions in the reaction zone can be transferred to the quark-gluon plasma (QGP) in the form of fluid vortices. Partons in the QGP will be polarized along the angular momentum through the spin-orbit interaction, the so-called “Globla Polarization”. After nearly two decades of exploration, experimental data on the global polarization of Λ hyperons and ϕ, K^*0 vector mesons in heavy-ion collisions have confirmed a new phenomenon of QGP global polarization, which has attracted widespread attention from researchers and become a new hot direction in the forefront of high-energy nuclear physics. This paper briefly describe the experimental measurements of global polarization in heavy-ion collisions, focusing on the global polarization of Λ hyperons and the spin alignment of ϕ, K^*0 mesons, followed by a brief discussion of the physics information provided by the experimental data.