Study of $$\Lambda $$ Λ polarization in relativistic nuclear collisions at $$\sqrt{s_\mathrm {NN}}=7.7$$ s NN = 7.7 –200 GeV

Abstract

Abstract We present a calculation of the global polarization of $$\Lambda $$ Λ hyperons in relativistic Au–Au collisions at RHIC Beam Energy Scan range $$\sqrt{s_\mathrm {NN}}=7.7{-}200$$ s NN = 7.7 - 200 GeV with a $$3+1$$ 3 + 1 -dimensional cascade $$\,+\,$$ + viscous hydro model, UrQMD $$\,+\,$$ + vHLLE. Within this model, the mean polarization of $$\Lambda $$ Λ 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 $$\Lambda $$ Λ polarization due to the decay of higher mass hyperons.

Keywords

• Collision Energy
• Total Angular Momentum
• Spin Vector
• Hydrodynamic Evolution
• Global Polarization