  A two phase cascade is presented for the treatment of ultra-high energy
ion-ion collisions at energies from 17-200 GeV. First a high energy, fast
cascade is performed, in which original baryons and freed hard partons, if any,
collide. This stage ignores energy loss from soft (slow) processes. In this
first version no hard processes, aside from Drell-Yan production, are included.
The space-time history of the hard phase is then used as input to reconstruct
soft energy-loss, which occurs over a longer time scale. Soft meson production
is therefore treated as coherent over groups of interacting nucleons. Two body
data, though, are used extensively to guide the reinitialisation of the
cascade, which satisfies conservation laws for charge, strangeness and of
course, energy-momentum. A second phase, low energy cascade is finally carried
out among the products of the hard cascade. The model selected to describe
elementary hadron-hadron collisions in the soft cascade incorporates generic
mesons and baryons, which are the agents for rescattering. We imagine a
constituent quark model applies, with generic mesons consisting of an excited
quark-antiquark pair, and generic baryons constructed from three quarks. The
chief result is a reconciliation of the important Drell-Yan measurements,
indicating high-mass lepton pairs are produced as if no energy is lost from the
nucleons, with the apparent success of a purely hadronic, soft cascade in
describing nucleon stopping and meson production in heavy ion experiments at
the CERN SPS.
