Momentum dependence of $\varphi$ meson's spin alignment

Abstract

We study the rapidity and azimuthal angle dependences of the global spin alignment ${\rho }_{00}$ for $\varphi$ mesons with respect to the reaction plane in Au+Au collisions at RHIC by the relativistic coalescence model in the spin transport theory. The global spin alignment of $\varphi$ mesons arises from local fluctuations of strong force fields whose values are extracted from the STAR's data. The calculated results show that ${\rho }_{00}<1/3$ at the rapidity $Y=0$, and then it increases with rapidity and becomes ${\rho }_{00}>1/3$ at $Y=1$. Such a rapidity dependence is dominated by the relative motion of the $\varphi$ meson in the bulk matter. We also give prediction for the azimuthal angle dependence of ${\rho }_{00}$ at different rapidities.

Comments: RevTex 4, 5 pages, 4 figures