Takafumi Niida (U of Tsukuba) Fastest swirling fluid created in heavy-ion collisions

Relativistic heavy-ion collisions are performed to understand the hot and dense QCD matter, i.e, quark-gluon plasma which was a state at the early universe just after the Big Bang. In non-central collisions, the system carries a large orbital angular momentum which leads to particle polarization. Recent observation of hyperon global polarization reveals that the matter created in the collisions is spinning the fastest ever observed, of the order of \omega~10^{21} 1/s. Further studies show that non-trivial velocity field due to the collective expansion of the system leads to more complex vorticities. Also, the observed particle polarization is closely related to chiral anomalous effects such as chiral magnetic/vortical effects, an electric charge separation along the initial magnetic field or the angular momentum in the presence of nonzero quark chirality. In this talk, recent results on hyperon polarization measurements in heavy-ion collisions will be presented and the physics implications will be discussed.