Study of [equation] polarization in relativistic nuclear collisions at [equation] –200?GeV

摘要

We present a calculation of the global polarization of (Lambda ) hyperons in relativistic Au–Au collisions at RHIC Beam Energy Scan range (sqrt{s_mathrm {NN}}=7.7{-}200)?GeV with a (3+1)-dimensional cascade(,+,)viscous hydro model, UrQMD(,+,)vHLLE. Within this model, the mean polarization of (Lambda ) in the out-of-plane direction is predicted to decrease rapidly with collision energy from a top value of about 2% at the lowest energy examined. We explore the connection between the polarization signal and thermal vorticity and estimate the feed-down contribution to (Lambda ) polarization due to the decay of higher mass hyperons.