Speaker
Description
In relativistic heavy ion collisions, the collective behaviors of deconfined quarks and gluons characterized by the hadron spectra and flow reveal the formation of quark gluon plasma (QGP), which can be macroscopically described by relativistic hydrodynamics with the transport coefficients governed by the underlying strong interaction. Recent measurements of the global spin polarization of Lambda hyperons further indicate the presence of strong vorticity of the rotating QGP and manifest the relativistic Barnett effect at the subatomic scale. However, it is elusive how we could further explore the microscopic properties of a QCD medium through spin-related observables. Recently, the measured spin alignment phenomena of vector mesons cannot be simply explained by the vorticity, which may lead to such a new opportunity. Microscopically, a considerable number of soft gluons, in the QGP phase or even in the glasma phase as its precursor with overpopulated gluons in the color-glass-condensate effective theory, may be delineated by fluctuating chromo-electromagnetic fields (or color fields for short). We will discuss how such color fields may potentially result in the spin alignment through the anisotropic spin correlation of the quark and antiquark forming a vector meson via quark coalescence. Also, the pertinent effects from color-field correlators with anisotropic quark flow could give rise to local spin polarization of $\Lambda$ hyperons along the beam direction. Consequently, we may employ the spin transport phenomena to probe the microscopic interaction of QCD matter in high-energy nuclear collisions.