Strangeness enhancement in Cu-Cu and Au-Au collisions at √s =200GeV

We report new STAR measurements of midrapidity yields for the Λ, Λ̄, KS0, Ξ , Ξ , Ω , Ω particles in Cu+Cu collisions at √s =200GeV, and midrapidity yields for the Λ, Λ̄, KS0 particles in Au+Au at √s = 200GeV. We show that, at a given number of participating nucleons, the production of strange hadrons is higher in Cu+Cu collisions than in Au+Au collisions at the same center-of-mass energy. We find that aspects of the enhancement factors for all particles can be described by a parametrization based on the fraction of participants that undergo multiple collisions.