  The deconfinement transition and the hadronization mechanism at high energy
are related to the quark-antiquark string breaking and the corresponding
temperature depends on the string tension $\sigma$. In the Unruh scheme of
hadron production it turns out $T = \sqrt{\sigma/2\pi}$, with $\sigma \simeq
\E$, the vacuum energy density. In heavy ion collisions at lower energy, i.e.
large baryonchemical potential, $\mu_B$, the dynamics is dominated by Fermi
statistics and baryon repulsion. However one can still consider $\E$ as the
relevant physical scale and its evaluation as a function of the baryon density,
in a nuclear matter approach, gives dynamical information on the $\mu_B$
dependence of the hadronization temperature and on the value of the critical
end point in the $T-\mu_B$ plane.
