Spontaneous CP violation at finite temperature in the MSSM

By studying the effective potential of the MSSM at finite temperature, we find that CP can be spontaneously broken in the intermediate region between the symmetric and broken phases separated by the bubble wall created at the phase transition. This type of CP violation is necessary to have a bubble wall profile connecting CP conserving vacua, while violating CP halfway and generating sufficient baryon number without contradiction of the experimental bounds on CP violation. Several conditions on the parameters in the MSSM necessary for CP to be broken in this manner are found.