  The STAR Beam Energy Scan program has found a difference in the global
polarization of $\Lambda$s and $\bar{\Lambda}$s produced in $Au+Au$ collisions.
This difference is larger for lower center of mass collision energies. In this
work we show that a two-component source, consisting of a high density core and
a lower density corona, can describe quantitatively the $\Lambda$ and
$\bar{\Lambda}$ polarization as a function of collision energy.
