Momentum dependence of the spin alignment of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ϕ</mml:mi></mml:math> meson
Xin-Li Sheng, Shi Pu, Qun Wang
Abstract
We study the rapidity and azimuthal angle dependences of the global spin alignment ${\ensuremath{\rho}}_{00}$ for $\ensuremath{\phi}$ mesons with respect to the reaction plane in $\mathrm{Au}+\mathrm{Au}$ collisions at the BNL Relativistic Heavy Ion Collider by the relativistic coalescence model in the spin transport theory. The global spin alignment of $\ensuremath{\phi}$ mesons arises from local fluctuations of strong force fields whose values are extracted from the STAR's data. The calculated results show that ${\ensuremath{\rho}}_{00}<1/3$ at the rapidity $Y=0$, and then it increases with rapidity and becomes ${\ensuremath{\rho}}_{00}>1/3$ at $Y=1$. Such a rapidity dependence is dominated by the relative motion of the $\ensuremath{\phi}$ meson in the bulk matter. We also give a prediction for the azimuthal angle dependence of ${\ensuremath{\rho}}_{00}$ at different rapidities.