Baryogenesis and the Thermalization Rate of Stop

We take the first steps towards the complete computation of the thermalization rate of the supersymmetric particles involved in electroweak baryogenesis by computing the thermalization rate of the right-handed stop from the imainary part of the two-point Green function. We use improved propagators including resummation of hard thermal loops. The thermalization rate is computed at the one-loop level in the high temperature approximation as a function of $M_{\tilde t_R}(T)$. We also give an estimate for the magnitude of the two-loop contributions which dominate the rate for small $M_{\tilde t_R}(T)$. If the stop is non-relativistic with $M_{\tilde t_R}(T)\gg T$, thermalization takes place by decay and is very fast.