Enhanced electroweak radiative corrections in SUSY and precision data

Enhanced radiative corrections generated in SUSY extensions of the Standard Model make the fit of the precision data ($Z$-boson decay parameters and $W$-boson mass) worse. This negative effect is washed out for heavy enough squarks due to decoupling property of SUSY models. We find that even for light squarks the enhanced radiative corrections can be small. In this case substantial $\tilde{t}_L \tilde{t}_R$ mixing is necessary.