  For central heavy ion collisions at the RHIC energy, the entropy per unit
rapidity dS/dy at freeze-out is extracted with minimal model dependence from
available experimental measurements of particle yields, spectra, and source
sizes estimated from two-particle interferometry. The extracted entropy
rapidity density is consistent with lattice gauge theory results for a
thermalized quark-gluon plasma with an energy density estimated from transverse
energy production at RHIC.
