Speaker
Description
Hyperon polarization observables are unique and important tools to study QCD spin dynamics, including spin transfer during hadronization, and the complex vortical structures of the QGP. With the high-statistics data collected by the CMS experiment, we present the measurements of polarization along the beam direction ($P_z$) for $\Lambda$ and $\bar{\Lambda}$ particles in pPb collisions at $\sqrt{s_{NN}}= 8.16$ TeV. The observed $P_z$ dependence on charged-particle multiplicity and transverse momentum cannot be described by existing hydrodynamic models incorporating vorticity effects, which successfully reproduce $P_z$ measurements in nucleus--nucleus collisions. We also report the first spin correlation results for $\Lambda$$\Lambda$, $\Lambda$$\bar{\Lambda}$, and $\bar{\Lambda}$$\bar{\Lambda}$ pairs in pp collisions at $\sqrt{s}= 13$ TeV and pPb collisions at $\sqrt{s_{NN}}= 8.16$ TeV as functions of the hyperon pair spatial distance ($\Delta R=\sqrt{\Delta\eta^{2}+\Delta\phi^{2}}$). These results provide new insights into hadronization dynamics and collective spin phenomena in high-energy hadronic collisions.
