  Kinematic edges in cascade decays provide a probe of the masses of new
particles. In some new physics scenarios the decay chain involves intermediate
particles of different flavors that can mix and oscillate. We discuss the
implication of such oscillation, and in particular its interplay with the
non-zero widths of the particles. We derive explicit formulae for differential
decay rates involving both non-zero widths and oscillation, and show that in
the case where the mass difference between the intermediate particle is of the
order of their widths, both oscillation and width effects are important. An
examination of the physical observables contained in these differential decay
rates is provided. We calculate differential decay rates for cases in which the
intermediate particles are either scalars or fermions.
