Vorticity in the QGP liquid and hyperon polarization at the RHIC BES energies

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We calculate the polarization of Λ hyperons in Au-Au collisions at RHIC Beam Energy Scan range √s NN=7.7,, 200 GeV in a state-of-the-art 3+1 dimensional cascade + viscous hydro model vHLLE+UrQMD. We find that the polarization of Λ in the out-of-plane direction decreases substantially with collision energy. We explore the connection between the polarization signal and thermal vorticity and discuss the feed-down and hadronic rescattering effects on the mean polarization of all produced Λ hyperons.