Measurement of global spin alignment of $K^{*0}$and $\phi$ 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 $K^{*0}$ 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 $K^{*0}$ results are compared to that of $\phi$ meson. At low-$p_{\mathrm{T}}$ region and midcentral collisions, the $K^{*0}$ $\rho_{00}$ is found to be smaller than 1/3 with about 4$\sigma$ significance, while that of $\phi$ 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.