Some problems concerning ultrarelativistic nucleus interactions

The described analysis of JACEE events is, of course, extremely rough and based on some arbitrary assumptions. But it demonstrates possibilities offered by observations of such events. At the same time it is evident that a better theoretical basis is needed. While the solution of hydrodynamical equations with initial conditions fixed in the Landau fashion gives the Gausian rapidity distribution with the flow in which approximately v ≅ x/t, in the papers it was proposed to consider the strict solution of the equations with v = x/t. It corresponds to different initial conditions and gives the rapidity plateau. This scaling solution was accepted as a starting point in many subsequent works. However, this solution needs to be properly adjusted to the external vacuum boundary. The problem was investigated and it was shown that the tail regions behave as particle-like formations, or as pistons, their masses changing during the expansion due to exchange of momentum with the central part. This shows how important it is to better understand the interaction of leading fireballs with cental quasiplateau