IMPLICATIONS OF A LIGHT STOP FOR THE SPONTANOUS CP BREAKING AT FINITE-TEMPERATURE IN A NONMINIMAL SUPERSYMMETRIC MODEL

We study the implications of a light stop for the spontaneous CP break ing at finite temperature in the Higgs sector of the Minimal Supersymm etric Standard Model with a gauge singlet. Assuming CP conservation at zero temperature, we show that the presence of a large mixing between the left- and the right-handed stops can trigger easily the spontaneo us breaking of CP inside the bubbles nucleated during the electroweak phase transition. This allows to avoid the fine-tuning among the vacuu m expectation values in the region of interest for the generation of t he baryon asymmetry, namely the bubble walls, which has been recently analized.