Study of Lambda polarization in relativistic nuclear collisions at sqrt{s}_NN = 7.7-200 GeV

TL;DR

This paper models the global polarization of Lambda hyperons in relativistic nuclear collisions across a range of energies, predicting a decrease in polarization with increasing collision energy and exploring underlying mechanisms.

Contribution

It introduces a comprehensive 3+1D cascade + viscous hydro + cascade model to predict Lambda polarization across energies, linking polarization to thermal vorticity and decay contributions.

Findings

Lambda polarization decreases rapidly with collision energy.

Predicted polarization is about 2% at the lowest energy.

Decay of higher hyperons contributes to Lambda polarization.

Abstract

We present a calculation of the global polarization of Lambda hyperons in relativistic Au-Au collisions at RHIC Beam Energy Scan range sqrt{s}_NN = 7.7 - 200 GeV with a 3+1 dimensional cascade + viscous hydro + cascade 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.