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

Abstract

We calculate the polarization of $\Lambda$ hyperons in Au-Au collisions at RHIC Beam Energy Scan range $\sqrt{s_{\mathrm{NN}}}=7.7,\dots ,200$ GeV in a state-of-the-art 3+1 dimensional cascade + viscous hydro model vHLLE+UrQMD. We find that the polarization of $\Lambda$ 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 $\Lambda$ hyperons.

Comments: proceedings of Strangeness in Quark Matter 2016 conference, 27 June - 1 July 2016, Berkeley