  Based on the chiral kinetic approach using initial conditions from a
multiphase transport model, we study the spin polarizations of quarks and
antiquarks in non-central heavy ion collisions at the Relativistic Heavy Ion
Collider. Because of the non-vanishing vorticity field in these collisions,
quarks and antiquarks are found to acquire appreciable spin polarizations in
the direction perpendicular to the reaction plane. Converting quarks and
antiquarks to hadrons via the coalescence model, we further calculate the spin
polarizations of Lambda and anti-Lambda hyperons and find their values
comparable to those measured in experiments by the STAR Collaboration.
