Is the existence of a softest point in the directed flow excitation   function an unambiguous signal for the creation of a quark-gluon plasma?
  The excitation function of the in-plane directed flow of nucleons is studied within a non-equilibrium transport approach. It is demonstrated that a local minimum in the excitation function of the directed flow develops, which is not related to a transition into a quark-gluon plasma (QGP) phase. It is a consequence of the dynamical softening of the underlying equation of state, due to the onset of resonance matter and particle production. Thus, the interpretation of this minimum as a 'smoking gun' signature for the creation of a QGP is premature. 
Marcus Bleicher and J\"org Aichelin