Chaotic scattering is a branch of chaos theory dealing with scattering systems displaying a strong sensitivity to initial conditions.  In a classical scattering system there will be one or more impact parameters, b, in which a particle is sent into the scatterer.  This gives rise to one or more exit parameters, y, as the particle exits towards infinity.  While the particle is traversing the system, there may also be a delay time, T—the time it takes for the particle to exit the system—in addition to the distance travelled, s. In certain systems (e.g. "billiard-like" systems in which the particle undergoes lossless collisions with hard, fixed objects) the two will be equivalent—see below.  In a chaotic scattering system, a minute change in the impact parameter, may give rise to a very large change in the exit parameters.