Collective motion in selected central collisions of Au on Au at 150<i>A</i>MeV

Using the FOPI facility at GSI Darmstadt complete data of Au on Au collisions at 150A MeV were collected for charged products (Z=1--15) at laboratory angles 1\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\mathrm{\ensuremath{\Theta}}}_{\mathrm{lab}}$\ensuremath{\le}30\ifmmode^\circ\else\textdegree\fi{}. Central collisions were selected by applying various criteria. The kinetic energy spectra of fragments from an isolated midrapidity source are investigated in detail for center-of-mass angles 25\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\mathrm{\ensuremath{\Theta}}}_{\mathrm{c}.\mathrm{m}.}$\ensuremath{\le}45\ifmmode^\circ\else\textdegree\fi{}. The heavy products (Z\ensuremath{\ge}3) are used to determine the collective energy which is found to be at least 10A MeV.