Spin alignment of vector mesons in heavy-ion collision

Abstract

We give a brief review on the spin alignment induced by the strong field and the shear-stress tensor. In experiments, a significant positive deviation from 1/3 is observed for the $\ddot{I}•$ meson, which can be explained by the anisotropy of the strong field fluctuation in the meson's rest frame, while the anisotropy is mainly a consequence of the motion of meson relative to the quark-gluon plasma. On the other hand, the shear-induced spin alignment is of the order $10^{-4}\sim 10^{-5}$ if the magnitude of thermal shear tensor is $10^{-2}$.

4 pages, 2 figures; proceedings of the The 10th Asian Triangle Heavy-Ion Conference (ATHIC 2025), Berhampur, Odisha, India, 13-16 Jan. 2025