Heavy ion reactions and the quark-gluon plasma

The Quark-Gluon Plasma (QGP) with its unobservable constituents is less tractable than the liquid and gas phases of low energy nuclear matter, which both decay to nuclear fragments. The signatures approach has all in all not been very successful, be it because no QGP is formed at AGS and SPS energies, or because the signatures are not specific enough. A likely exception are the hard probes: the comprehensive psi and psi' results from p-A, S-U and Pb-Pb collisions are hard to reconcile with pure hadronic absorption. Transverse how systematics and new d, t, (p) over bar and (d) over bar data point to a constant 150 MeV freeze-out temperature, from p-p to Pb-Pb. But this is hard to reconcile with a nearly constant multiplicity per interacting baryon. Where does the increased energy dissipation go?