Energy dependence of rescattering effect on vector mesons spin alignment at RHIC

Abstract

Spin alignment of vector mesons in heavy-ion collisions provides a novel probe of quark polarization and hadronization mechanism in quark-gluon plasma. Hadronic rescattering may affect the measured spin alignment of vector mesons due to non-uniform rescattering probability in non-central heavy-ion collisions. Using the UrQMD model, we systematically investigated the hadronic rescattering effect on the measurement of $\rho_{00}$, the spin alignment parameter, for $K^{*0}$, $\phi$, and $\rho^{0}$ mesons in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7 - 200 GeV. Our results reveal that the measurable $\rho_{00} - 1/3$ remains unaffected for $\phi$, while shows significantly negative (positive) deviations for $K^{*0}$ and $\rho^0$ with respect to the reaction (production) plane. Quantitatively, the maximum deviation reaches $-0.0056$ ($0.0268$) for $K^{*0}$ and $-0.0122$ ($0.0414$) for $\rho^{0}$ with respect to the reaction (production) plane. Notably, the deviations in $\rho_{00}$ for both $K^{*0}$ and $\rho^{0}$ increase monotonically with increasing collision energy. These findings underscore the critical necessity of accounting for rescattering effects when interpreting spin alignment measurements of short-lived vector mesons in heavy-ion collisions.