Diffusion and Decoherence of Squarks and Quarks During the Electroweak Phase Transition

To estimate the diffusion constant $D$ of particles in a plasma, we develop a method that is based on the mean free path $\lambda$ for scatterings with momentum transfer $q >~ T$. Using this method, we estimate $\lambda$ and $D$ for squarks and quarks during the electroweak phase transition. Assuming that Debye and magnetic screening lengths provide suitable infrared cutoffs, our calculations yield $\lambda <~ 18/T$ and $D <~ 5/T$ for both squarks and quarks. Our estimate of $\lambda$ suggests that suppressions of charge transport due to decoherence of these strongly interacting particles during the electroweak phase transition are not severe and that these particles may contribute significantly to electroweak baryogenesis.