large rapidities. Faster fluid elements need a longer time to cool down to the same temperatures than the cells at midrapidity since the hydrodynamic calculation is performed in the center-of-mass frame of the collision. At higher energies the isochronous hypersurface increasingly differs from an iso-$\tau$ hypersurface ($\tau$ is the proper time). To mimic an iso-$\tau$ hypersurface we therefore freeze out transverse slices, of thickness $\Delta z = 0.2
$fm, whenever all cells of that slice fulfill our freeze-out criterion. For each slice we apply the isochronous procedure described above separately. By doing this we obtain a rapidity independent freeze-out temperature even for the highest beam energies. For lower energies ($E_{lab}\lesssim 80A$ GeV) the two procedures yield very similar results for the temperature distributions. The hydrodynamic fields are then again mapped to particle degrees of freedom via the Cooper-Frye equation on this new hypersurface. In the following we will refer to this procedure as “gradual freeze-out”(GF). A more detailed description of the hybrid model including parameter tests and results for multiplicities and spectra can be found in [@Petersen:2008dd].

Serving as an input for the hydrodynamical calculation the EoS strongly influences the dynamics of an expanding system. In this work we use 