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

TL;DR

This paper investigates how the spin alignment of $$ mesons varies with rapidity and azimuthal angle in heavy-ion collisions, using a relativistic coalescence model informed by experimental data.

Contribution

It introduces a model to describe the rapidity and azimuthal angle dependence of $$ meson spin alignment based on local strong force fluctuations and relativistic coalescence.

Findings

$$ meson spin alignment $ ho_{00}$ decreases below 1/3 at mid-rapidity.

$$ meson spin alignment increases with rapidity, exceeding 1/3 at $Y=1$.

Predictions are provided for azimuthal angle dependence of $ ho_{00}$ at various rapidities.

Abstract

We study the rapidity and azimuthal angle dependences of the global spin alignment $\rho_{00}$ for $\phi$ 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 $\phi$ 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 $\phi$ meson in the bulk matter. We also give prediction for the azimuthal angle dependence of $\rho_{00}$ at different rapidities.