Semiclassical spin diffusion model compared to quantum calculation of depolarization in electron storage rings

The Chao formalism of the semiclassical spin diffusion model is compared to the Hand-Skuja quantum calculation of equilibrium polarization in electron storage rings. This spin diffusion model, considering electron-energy jumps as well as angular recoils, exactly reproduces the main quadratic terms in the quantum result which are responsible for beam depolarization. This comparison justifies the use of this semiclassical model to first order in the spin motion and shows its limitations. (orig.)