Global spin polarization of multistrange hyperons and feed-down effect in heavy-ion collisions

TL;DR

This study calculates the global spin polarization of hyperons in heavy-ion collisions using a transport model, revealing a specific polarization hierarchy and the impact of decay feed-down effects, which can be tested experimentally.

Contribution

It provides the first detailed calculation of hyperon polarization hierarchy and feed-down effects across a range of collision energies.

Findings

Polarizations follow the relation P_{Ω^-} ≈ 5/3 P_{Ξ^-} ≈ 5/3 P_{Λ}

Feed-down effects significantly influence the observed polarization values

Final polarization order is P_{Ω^-} > P_{Ξ^-} > P_{Λ}

Abstract

Global spin polarization of hyperons is an important observable to probe the vorticity of the quark-gluon plasma produced in heavy-ion collisions. We calculate the global polarizations of $\Lambda$, $\Xi^-$, and $\Omega^-$ in Au+Au collisions at energies $\sqrt{s_\text{NN}}=$ 7.7--200 GeV based on a multiphase transport model. Our calculations suggest that their primary global polarizations fulfill $P_{\Omega^-}\simeq 5/3P_{\Xi^-}\simeq 5/3P_\Lambda$. We also estimate the feed-down effect of particle decay on the global polarization. With the feed-down effect taken into account, the global polarizations of $\Lambda$ and $\Xi^-$ are clearly separated, and the final global polarizations are in the ordering: $P_{\Omega^-}>P_{\Xi^-}>P_\Lambda$. Such a relation can be tested in experiments, which will provide us more information about the global polarization mechanism.