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Global polarization of $\Xi$ and $\Omega$ hyperons in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV

The STAR collaboration
Adam, J. , Adamczyk, L. , Adams, J.R. , Adkins, J.K. , Agakishiev, G. , Aggarwal, M.M. , Ahammed, Z. , Alekseev, I. , Anderson, D.M. , Aparin, A.
Phys.Rev.Lett. 126 (2021) 162301, 2021.
https://doi.org/10.17182/hepdata.100234

Abstract (data abstract)
Global polarization of $\Xi$ and $\Omega$ hyperons has been measured for the first time in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The measurements of the $\Xi^-$ and $\bar{\Xi}^+$ hyperon polarization have been performed by two independent methods, via analysis of the angular distribution of the daughter particles in the parity violating weak decay $\Xi\rightarrow\Lambda+\pi$, as well as by measuring the polarization of the daughter $\Lambda$-hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over $\Xi^-$ and $\bar{\Xi}^+$, is measured to be $\langle P_{\Xi}\rangle$ = 0.47 $\pm$ 0.10 (stat.) $\pm$ 0.23 (syst.) % for the collision centrality 20%-80%. The $\langle P_{\Xi}\rangle$ is found to be slightly larger than the inclusive $\Lambda$ polarization and in reasonable agreement with a multiphase transport model. The $\langle P_{\Xi}\rangle$⟨PΞ⟩ is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of $\Omega$, $\langle P_{\Omega}\rangle$ = 1.11 $\pm$ 0.87 (stat.) $\pm$ 1.97 (syst.) % was obtained by measuring the polarization of daughter $\Lambda$ in the decay $\Omega\rightarrow\Lambda+K$, assuming the polarization transfer factor $C_{\Omega\Lambda}$ = 1.

  • Figure 2.0

    10.17182/hepdata.100234.v1/t1

    $\Xi$ and $\Omega$ global polarization in Au+Au collisions at 200 GeV. Decay parameter from PDG2020, $\alpha_{\Xi}$=-$\alpha_{\bar{\Xi}}$=-0.401, is used.

  • Figure 2.1

    10.17182/hepdata.100234.v1/t2

    The energy dependence of $\Lambda$ and $\bar{\Lambda}$ global polarization. Note that the results from previous measurements are rescaled using updated...

  • Figure 3.0

    10.17182/hepdata.100234.v1/t3

    Centrality dependence of $\Xi$ global poalrization in Au+Au collisions at 200 GeV. Decay parameter from PDG2020, $\alpha_{\Xi}$=-$\alpha_{\bar{\Xi}}$=-0.401, is used.

  • Figure 3.1

    10.17182/hepdata.100234.v1/t4

    Centrality dependence of $\Lambda$ global polarization in Au+Au collisions at 200 GeV. Note that the results from previous measurement are...

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