Diffusion of two populations of retrograde test stars of different individual mass. The two populations are initially distributed according to the same PDF, illustrated with the black histogram. The evolution of each test star is described by the Langevin equation associated with the Fokker-Planck Eq. (72). After a time ΔT = 200, the PDF of the light population (of individual mass μ_t = μ_⋆) is given by the red histogram, while the heavy population (of individual mass μ_t = 10μ_⋆) follows the PDF given by the blue histogram. Because of the prefactor (μ_t/μ_⋆) present in Eq. (72), populations of different individual mass do not follow the same stochastic motions, and the system undergoes a mass segregation. Light (red) wires tend to become less eccentric and heavy (blue) wires tend to become more eccentric.