  The formation and propagation of high-density compression waves, e.g. Mach
shock waves, in cold nuclear matter is studied by simulating high-energy
nucleus-nucleus collisions of Ne with U in the energy range from E_lab = 0.5
AGeV to 20 AGeV. In an ideal hydrodynamic approach, the high-density shock wave
created by the small Ne nucleus passing through the heavy U nucleus is followed
by a slower and more dilute Mach shock wave which causes conical emission of
particles at the Mach cone angle. The conical emission originates from
low-density regions with a small flow velocity comparable to the speed of
sound. Moreover, it is shown that the angular distributions of emitted baryons
clearly distinguish between a hydrodynamic approach and binary cascade
processes used in the Ultra-relativistic Quantum Molecular Dynamics (UrQMD)
transport model.
