Abstract: In this talk, we consider the Kac stochastic particle system linked to the spatially homogeneous Boltzmann equation for true hard potentials. We derive a rate of propagation of chaos, demonstrating the convergence of the particle system to the unique solution of the Boltzmann equation. Specifically, we provide estimates for the expectation of the squared Wasserstein distance, with a quadratic cost, between the empirical measure of the particle system and the Boltzmann solution. This presentation is based on joint work with Liping Xu and An Zhang.