Speaker
Description
The hot and dense matter created in non-central heavy-ion collisions is supposed to have the initial angular momentum carried by two colliding nuclei. Some fraction of the angular momentum might be transferred to the global polarization of spin of particles composing the medium due to spin-orbit coupling. The STAR experiment has made the first observation of \Lambda hyperon polarization in Au+Au collisions at \sqrt{s_{NN}} = 7.7 — 39 GeV, showing a possible difference between \Lambda and \bar{\Lambda}. The difference might be the effect of a magnetic coupling to spin and thus could be a possible constraint on the magnitude and life time of the initial magnetic field. These results are quite important to further understand the role of the thermal vorticity in heavy-ion collisions. It is closely related to the chiral phenomena like the Chiral Magnetic Effect and Chiral Vortical Effect, and also likely related to other observables such as the directed flow and elliptic flow.
We present recent experimental results on the global polarization and discuss their implications. New results for 200 GeV and LHC energies will be also discussed. Furthermore we present results of the directed flow to discuss the initial tilt of the source and density fluctuations with a possible connection to the vorticity.