  In this paper, we consider the Kac stochastic particle system associated to
the spatially homogeneous Boltzmann equation for true hard potentials. We
establish a rate of propagation of chaos of the particle system to the unique
solution of the Boltzmann equation. We use a probabilistic coupling method and
give, under suitable assumptions on the initial condition, a rate of
convergence of the empirical measure of the particle system to the solution of
the Boltzmann equation for this singular interaction.
