  We simulate the fragmentation processes in the \alAu collisions at the
bombarding energy 5 GeV/u using the simplified RQMD approach. The statistical
decay calculation is connected to obtain the final state. >From the simulation
we find that the residual nucleus created by this collision has a annular
eclipse shape, and then expands more strongly to the transverse direction than
to the beam-direction. Then the angular-distribution of the intermediate mass
fragments has a sideward peak; this result explains the experimental result.
