Stopping and radial flow in central $^{58}$Ni + $^{58}$Ni collisions between 1A and 2A GeV

The production of charged pions, protons and deuterons has been studied in central collisions of 58Ni on 58Ni at incident beam energies of 1.06, 1.45 and 1.93 AGeV. The dependence of transverse-momentum and rapidity spectra on the beam energy and on the centrality of the collison is presented. It is shown that the scaling of the mean rapidity shift of protons established for AGS and SPS energies is valid down to 1 AGeV. The degree of nuclear stopping is discussed; the IQMD transport model reproduces the measured proton rapidity spectra for the most central events reasonably well, but does not show any sensitivity between the soft and the hard equation of state (EoS). A radial flow analysis, using the midrapidity transverse-momentum spectra, delivers freeze-out temperatures T and radial flow velocities beta_r which increase with beam energy up to 2 AGeV; in comparison to existing data of Au on Au over a large range of energies only beta_r shows a system size dependence.