Speaker
Description
As a conserved quantity in the evolution of the quark-gluon plasma (QGP) created in heavy-ion collisions, the total angular momentum consists of two sectors: the orbital angular momentum (OAM) caused by kinetic motion, and the intrinsic spin angular momentum of quarks and gluons. In a heavy-ion collision event, the system starts with finite OAM but un-polarized spin density (unless prepared specifically). Microscopic scattering processes allow a coupling between these two components. Therefore, spin polarization can eventually develop that may have a non-trivial influence on the QGP evolution. In the current hydrodynamic frameworks, the stress tensor $T^{\mu\nu}$ is assumed to be symmetric, hence OAM and spin are conserved independently, and the spin effect is mostly neglected. A hydrodynamic theory, with the aforementioned spin polarization effect properly taken into account, is required, especially for quantitative studies of the polarization rate of observed hadrons, e.g. $\Lambda$-hyperon. The latter has been observed in RHIC experiment, serving as an evidence of the most vortical fluid in the universe.
In this work, we start with chiral kinetic theory and construct the spin hydrodynamic framework for a chiral spinor system. We obtain the equations of motion of second-order dissipative relativistic fluid dynamics with non-trivial spin polarization density. In a chiral spinor system, the spin alignment effect could be treated in the same framework as for Chiral Vortical Effect (CVE). However, the fluid vorticity induces not only the CVE current but also asymmetric stress tensor as well as spin polarization of final state hadrons, all of which emerge as quantum corrections. The consequences for current measurements related to angular momentum observables will be discussed.
