Speaker
Description
In non-central heavy-ion collisions (HIC), the large initial angular momentum can induce a non-vanishing polarization for hadrons with non-zero spin. The global spin alignment of vector mesons, quantified by the $00^{th}$ element of spin density matrix $(\rho_{00})$, can offer information on the spin-orbital interactions of the QCD medium. Surprisingly large signal of vector meson ρ00 compared to hyperon spin polarization poses challenges to the conventional theoretical understanding of polarization in HIC. Preliminary observations from Beam Energy Scan (BES) of large deviations of $\rho_{00}$ from 1/3 for $\phi(1020)$ mesons can only be explained by introducing the vector meson strong force fields.
In this talk, we will review the details on global spin alignment of $\phi(1020)$ and $K^∗(892)$ using high statistics BES data of Au+Au collisions at RHIC and discuss its physics implication.
