The maximum lifetime of the quark-gluon plasma

The width ΔT of the deconfinement transition region is shown to influence strongly the flow structure in the (Landau) hydrodynamical expansion of a quark-gluon plasma. For a sharp first order transition ( ΔT = 0) the mixed phase is rather long-lived, with a lifetime that has a maximum when the initial energy density is at the phase boundary between mixed and pure quark-gluon matter. For increasing ΔT, however, the lifetime decreases rapidly. Hadromic matter, however, remains long-lived as a consequence of the rapid change in the degrees of freedom in the transition region and the corresponding "softening" of the equation of state.