  Motivated by realistic scattering processes of composite systems, we study
the dynamics of a two-particle bound system which is scattered at a mirror. The
physics of the scattering process will be discussed in the cases when only one
particle interacts directly with the mirror and when both particles are
scattered directly. It is shown that the coherence between the transmitted and
the reflected wave-packet becomes reduced due to the scattering process. When
both particles interact directly with the mirror, the system exhibits
long-lived resonances. The results should be of interest for interference
experiments with composite systems.
