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

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.

Comments: 6 pages, 3 figures. v2: discussion added