Supersymmetric Baryogenesis at the Electroweak Phase Transition

We study the possibility of baryogenesis in the case of supersymmetry breaking with large mixing between the $\chr$ and $\tr$ or $\ur$ and $\tr$ squarks resulting in one light right-handed up-type squark mass eigenstate. We argue that in this case the electroweak phase transition will be first order, and that large phases already present in the quark mass matrices can generate a baryon asymmetry of the correct magnitude without introducing any new phases specifically for this purpose. We study in detail a particular ansatz for supersymmetry breaking and CP violation where there is only one CP violating phase in the theory: in the up-type quark mass matrix. We study the constraints placed on this model by baryogenesis and flavor physics. This scenario has robust implications for low energy flavor phsyics including $D^0-\bar D^0$ mixing and an electric dipole moment for the neutron that are close to the experimental bounds, and CP violation in the $B-\bar B$ system that is different from that in the Standard Model