From the Glasma to the QCD Phase Boundary
  In this paper, I qualitatively discuss the matter formed in the fragmentation region of nuclear collisions at the highest energies. I argue that although the initial temperature and baryon number density can become very large, the ratio of initial baryon chemical potential to initial temperature is approximately independent of energy, when measured at a fixed rapidity measured from the end of the fragmentation region. This quantity is argued to be roughly invariant under expansion, and therefore the value measured at decoupling should be approximately the same as the initial value and largely independent of energy. The values of the initial temperature and initial baryon number are energy dependent and become large as the center of mass collision energy increases. 
Larry McLerran
hep-ph