  Dark matter halos are built from accretion and merging. During merging some
of the dark matter particles may be ejected with velocities higher than the
escape velocity. We use both N-body simulations and single-particle
smooth-field simulations to demonstrate that rapid changes to the mean field
potential are responsible for such ejection, and in particular that dynamical
friction plays no significant role in it. Studying a range of minor mergers, we
find that typically between 5-15% of the particles from the smaller of the two
merging structures are ejected. We also find that the ejected particles
originate essentially from the small halo, and more specifically are particles
in the small halo which pass later through the region in which the merging
occurs.
