Quark Diffusion and Baryogenesis at the Electroweak Phase Transition

Baryogenesis at the electroweak phase transition may take place through CP-violating reflections of quarks from expanding bubbles of the broken symmetry phase. We formulate and approximately solve the transport equations for the reflected quark asymmetries. The results are comparable to a previous Monte Carlo calculation and allow for analytic estimates of the baryon asymmetry $\Delta B$ when the bubble walls have a small velocity. Our method predicts no velocity-dependence for $\Delta B$ in the small $v$ limit, unlike results obtained from a simplified treatment based on the diffusion equation.