Hadron spectra and collective transverse flow in ultrarelativistic nuclear collisions

The transverse momentum (pT) spectra of various hadron species measured at Brookhaven in 14.5 A GeV Si+Au collisions and at CERN in 200 A GeV O+Au and S+Al collisions, are integrated in terms of a superposition of local thermal and global collective expansion at the point of particle freeze-out. Comparing spectra of particles with different masses allows for a separation of the thermal and flow components and thus a separate determination of the freeze-out temperature and the expansion velocity. By varying the initial energy and baryon density of the fireball, a particular initial fireball state was identified which simultaneously explains all the observed pT spectra. (Z.S.) 5 figs., 20 refs