Global polarization of Ξ and Ω hyperons in Au+Au collisions at sNN = 200 GeV

The STAR collaboration
Phys.Rev.Lett. 126 (2021) 162301, 2021.

Abstract (data abstract)
Global polarization of Ξ and Ω hyperons has been measured for the first time in Au+Au collisions at sNN = 200 GeV. The measurements of the Ξ and Ξ¯+ 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 ΞΛ+π, as well as by measuring the polarization of the daughter Λ-hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over Ξ and Ξ¯+, is measured to be PΞ = 0.47 ± 0.10 (stat.) ± 0.23 (syst.) % for the collision centrality 20%-80%. The PΞ is found to be slightly larger than the inclusive Λ polarization and in reasonable agreement with a multiphase transport model. The PΞ⟨PΞ⟩ is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of Ω, PΩ = 1.11 ± 0.87 (stat.) ± 1.97 (syst.) % was obtained by measuring the polarization of daughter Λ in the decay ΩΛ+K, assuming the polarization transfer factor CΩΛ = 1.

  • Figure 2.0

    10.17182/hepdata.100234.v1/t1

    Ξ and Ω global polarization in Au+Au collisions at 200 GeV. Decay parameter from PDG2020, αΞ=-αΞ¯=-0.401, is used.

  • Figure 2.1

    10.17182/hepdata.100234.v1/t2

    The energy dependence of Λ and Λ¯ 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 Ξ global poalrization in Au+Au collisions at 200 GeV. Decay parameter from PDG2020, αΞ=-αΞ¯=-0.401, is used.

  • Figure 3.1

    10.17182/hepdata.100234.v1/t4

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

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