  A quantum mechanical theory with time asymmetry intrinsic to states (or
observables) features the concept of an initial time of the state and thus a
preparation time of the physical system represented by the state. This special
time is investigated in the context of scattering theory, where, in standard
quantum mechanics, the physical meaning of a preparation time has remained
obscure. In an experiment, the preparation time corresponds to an ensemble of
times of scattering marking the times in the laboratory when one scattering
projectile interacts with one target quantum.
