Measurement of global spin alignment of $K^{\ast 0}$and $\varphi$ vector mesons using the STAR detector at RHIC

Abstract

We report the transverse momentum ($p_{\mathrm{T}}$) and centrality dependence of global spin alignment (${\rho }_{00}$) of $K^{\ast 0}$ vector meson at midrapidity ($|y|<0.5$) in Au + Au collisions at $\sqrt{s_{NN}}$ = 54.4 and 200~GeV with the STAR experiment at RHIC. The $K^{\ast 0}$ results are compared to that of $\varphi$ meson. At low-$p_{\mathrm{T}}$ region and midcentral collisions, the $K^{\ast 0}$ ${\rho }_{00}$ is found to be smaller than 1/3 with about 4$\sigma$ significance, while that of $\varphi$ meson is observed to be larger than 1/3 with about 3$\sigma$ significance. The ${\rho }_{00}$ results are compared between RHIC and LHC energies. The physics implication of our results is also discussed.

Comments: 4 pages, 4 figures. Quark Matter 2019 proceedings