Speaker
Baochi Fu
(Peking University)
Description
The measurement of spin polarization in heavy-ion collisions provide new insight into the properties of hot and dense QCD matter. We study the spin polarization generated by fluid gradients based on data-calibrated hydrodynamic simulations. In additional to the widely studied thermal vorticity effects, we identify an undiscovered contribution from the fluid shear. The expression of the shear-induced polarization (SIP) can be obtained by quantum kinetic equation and linear response theory. Based on a realistic hydrodynamic model, we compute the azimuthal angle dependence of polarization $P_y(\phi)$ and $P_z(\phi)$ including both thermal vorticity and shear effects. We find that SIP contribution always shows the same azimuthal angle dependence as experimental data and competes with the thermal vorticity effect. In the scenario that $\Lambda$ inherits and memorizes the spin polarization of strange quark, SIP wins the competition, and the resulting $P_y(\phi)$ and $P_z(\phi)$ agrees qualitatively with the experiment measurements.
Summary
We investigate a new mechanism to generate spin polarization (current) in heavy-ion collisions-—shear-induced polarization (SIP). The effects of thermal vorticity and newly discovered SIP on spin polarization is studied based on a realistic hydrodynamic model. SIP shows same azimuthal angle dependence with indispensable magnitude to the spin polarization analysis. If $\Lambda$ hyperon inherits and memorizes the spin polarization of strange quark, the azimuthal angle dependence of the spin polarization describes the experimental data qualitatively.
Primary author
Baochi Fu
(Peking University)
Co-authors
LongGang Pang
(Central China Normal University)
Dr
Shuai Liu
(IMP)
Yi Yin
(IMP)
慧超 宋
(Peking University)
