Evidence for a Blast Wave from Compressed Nuclear Matter

Abstract

Central collisions of heavy nuclei at cm. kinetic energies of a few hundred MeV per nucleon produce fireballs of hot, dense nuclear matter. Each fireball explodes, producing a blast wave of nucleons and pions. Several features of the observed cross sections for pions and protons from Ne on Na F at 0.8 GeV/nucleon (lab) are explained by the blast wave, but contradict earlier, purely thermal models. The available energy is equally divided between translational energy of the blast, and thermal motion of the paritlces in the exploding matter.

Towards relativistic heavy ion collisions “by small steps towards the stars”

“…The development of the fireball in coordinate space (left) and in momentum space (right) is evident. As we mentioned previously, a detailed analysis also shows that complete thermalization is achieved, after only a few nucleonnucleon collisions (see also, Smith, 1977).…”

“…For head on collisions of uranium on uranium at a few hundred MeV/nucleon, three times normal density is reached. Com parable densities are also attained in more detailed cascade calculations (Smith, 1977), an example of which for calcium on calcium at 1 GeV/nucleon is shown in Fig. 3.4 (Cugnon, 1979).…”

“…The difference in ir-p temperatures cannot be Bolely due to the cooling effect of pion production, since only one pion is created for every 10 protons, with a mean energy (including the rest mass) of 240 MeV. Assuming equal numbers of TT~ and IT 0 , about 35 MeV per baryon goes into producing end accelerating pions, lowering the temperature to only 90 MeV (Siemens, 1979).…”

“…The additional cooling has been attributed to a "blast wave" (Siemens, 1979). It is a matter of ordinary experience that the sudden creation of hot, dense , 1976, 1979).…”

Progress in Collective Flow Studies from the Onset to Bevalac/SIS

“…and the intrinsic temperature (that is, in the flow frame, not the overall source frame) of the source. Such a scenario was considered to explain proton and pion spectra at 90" in the Ne+NaF reaction at 800 A-MeV [41]. However, only with the availability of the recent high quality data sets have systematic studies of the radial flow in heavy ion collisons been possible.…”