Abstract
The evolution of net-proton rapidity spectra with √<^SNN> in heavy relativistic systems is proposed as an indicator for local equilibration, longitudinal expansion, and deconfinement. Bell-shaped distributions in central collisions at AGS energies and double-humped nonequilibrium spectra at SPS show pronounced collective expansion. The broad midrapidity valley recently discovered at RHIC indicates longitudinal expansion of a locally equilibrated subsystem. In central Au-Au collisions at 200 GeV, fast local equilibration which is most likely due to deconfinement is estimated in a Relativistic Diffusion Model to occur for 14 per cent of the incoming baryons. A prediction is made for √<^SNN>=62.4GeV.
