  Using the FOPI detector at GSI Darmstadt, excitation functions of collective
flow components were measured for the Au+Au system, in the reaction plane and
out of this plane, at seven incident energies ranging from 100AMeV to 800AMeV.
The threshold energies, corresponding to the onset of sideward-flow (balance
energy) and squeeze-out effect (transition energy), are extracted from
extrapolations of these excitation functions toward lower beam energies for
charged products with Z>2. The transition energy is found to be larger than the
balance energy. The impact parameter dependence of both balance and transition
energies, when extrapolated to central collisions, suggests comparable although
slightly higher values than the threshold energy for the radial flow. The
relevant parameter seems to be the energy deposited into the system in order to
overcome the attractive nuclear forces.
