Precision tests of the MSSM

We present the results of a global fit to the electroweak observables in the MSSM in which, for the first time, all the (relevant) low energy parameters of the model are treated as independent variables. The best fit selects either very low or very large values of tan β and chargino (higgsino-like) and stop or/and the CP-odd Higgs boson are within the reach of LEP 2. Moreover, the best fit gives αs (Mz) = 0.114 ± 0.007, which is lower than the one obtained from the SM fits. The overall description of the electroweak data is better than in the SM. Those results follow mainly from the fact that in the MSSM one can increase the value of Rb ≡ Γz0→bbΓZ0→hadrons without modifying the SM predictions for other observables.