At the same time, lots of hard scattering models were proposed10)-12) and it is also well known that the calculations of perturbative QCD agree with Pt data in the large Pt region. 13 ) Shuryak 8 ) tried to explain such a complicated situation by considering the spacetime development of high energy collisions. After a hard collision the constituents go through each other and the system expands. When the extent of the system (or system duration) gets to the value of the mean free path, the thermodynamical description becomes reasonable and the system is able to be treated as a quark-gluon plasma. The medium Pt (Pt=1~5 GeV/c) spectrum is ex-