Rescattering effect on the measurement of K* spin alignment in heavy-ion collisions

TL;DR

This paper investigates how hadronic rescattering affects the measurement of K* meson spin alignment in heavy-ion collisions, revealing that rescattering can cause deviations comparable to or larger than the expected signals from global quark polarization.

Contribution

It demonstrates that rescattering effects significantly influence K* spin alignment measurements, which must be accounted for in experimental and theoretical analyses.

Findings

Rescattering causes deviations in $ ho_{00}$ up to -0.008 (reaction plane) and 0.03 (production plane).

Deviations are larger than those predicted by models based solely on global quark polarization.

Rescattering effects can mimic or obscure signals of quark polarization in experiments.

Abstract

Spin alignment of vector mesons in noncentral relativistic heavy ion collisions provides a novel probe of the global quark polarization and hadronization mechanism. In this paper, we discuss the spin alignment of a short-lived vector meson, namely K*, arising from the hadronic rescattering process using the UrQMD model. This spin alignment is not related to global quark polarization but cannot be distinguished from those arising from global quark polarization in experiments. The spin alignment parameter $\rho_{00}$ is found to deviate from 1/3 by up to -0.008 (0.03) with respect to the reaction (production) plane. These deviations are much larger than the expected signal from all the theoretical models implementing the conventional global quark polarization mechanism as well as the current experimental precision, and should be considered seriously when comparing measurements with theoretical calculations.