Vorticity in the QGP liquid and $\Lambda$ polarization at the RHIC Beam Energy Scan

Abstract

Polarization of $\Lambda$ hyperons and their antiparticles is calculated in a 3+1 dimensional viscous hydrodynamic model with initial state from UrQMD hadron/string cascade. We find that, along with recent results from STAR, the mean polarization at fixed centrality decreases as a function of collision energy from 1.5% at $\sqrt{s_{\mathrm{NN}}}=7.7$ GeV to 0.2% at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. We explore the effects which lead to such collision energy dependence, feed-down corrections and a difference between $\Lambda$ and $\bar{\Lambda }$.

Comments: contribution to proceedings of Quark Matter 2017, 5-11 February 2017, Chicago (IL)