Hadronic yields and yield ratios observed in Pb+Pb collisions at the SPS
energy of 158 GeV per nucleon are known to resemble a thermal equilibrium
population at T=180 +/- 10 MeV, also observed in elementary e+ + e- to hadron
data at LEP. We argue that this is the universal consequence of the QCD parton
to hadron phase transition populating the maximum entropy state. This state is
shown to survive the hadronic rescattering and expansion phase, freezing in
right after hadronization due to the very rapid longitudinal and transverse
expansion that is inferred from Bose-Einstein pion correlation analysis of
central Pb+Pb collisions.Comment: 10 pages, 2 figure
