HADRON SPECTRA FROM NUCLEAR COLLISIONS

We describe high energy nuclear collisions by a superposition of isotr opically decaying thermal sources (''fireballs'') of freeze-out temper ature T = 0.15 GeV. The longitudinal fireball superposition is taken a s boost-invariant, in a rapidity range determined by the average energ y loss of nucleons in p-p collisions. The transverse fireball motion i s assumed to be due to random walk initial state collisions; it is det ermined by p-A data and then extrapolated to central A-B interactions. We thus obtain parameter-free predictions for the rapidity and transv erse momentum spectra of hadrons produced in high energy nucleus-nucle us collisions. The results account fully for the observed broadening o f transverse momentum distributions, so that single-particle spectra r equire neither collective flow nor temperature increase.