Opening the window for electroweak baryogenesis

We perform an analysis of the behaviour of the electroweak phase transition in the Minimal Supersymmetric Standard Model, in the presence of light stops. We show that, in previously unexplored regions of parameter space, the order parameter upsilon(T-c)/T-c can become significantly larger than one, for values of the Higgs and supersymmetric particle masses consistent with the present experimental bounds. This implies that baryon number can be efficiently generated at the electroweak phase transition. As a by-product of this study, we present an analysis of the problem of colour breaking minima at zero and finite temperature and we use it to investigate the region of parameter space preferred by the best fit to the present precision electroweak measurement data, in which the left-handed stops are much heavier than the right-handed ones.