When Are Radiative Corrections Important in the Minimal Supersymmetric Model?

Precision electroweak measurements at LEP currently check the validity of the Standard Model to about one part in a thousand. Any successful model of physics beyond the Standard Model must be consistent with these observations. The impact of radiative corrections on the Minimal Supersymmetric Model (MSSM) is considered. The influence of supersymmetric particles on precision electroweak measurements is generally negligible since radiative corrections mediated by supersymmetric particles are suppressed by a factor of order $m_Z^2/M_{\rm SUSY}^2$ (where $M_{\rm SUSY}$ is the scale characterizing the scale of supersymmetric particle masses). However, there are a few pertinent exceptions. For example, the radiative corrections to the rare decay $b\to s\gamma$ from charged Higgs and supersymmetric particle exchange can be of the same order as the Standard Model contribution. Large radiative corrections also lead to modifications of MSSM tree-level (natural) relations. The largest corrections of this type occur in the MSSM Higgs sector and are enhanced by powers of the top quark mass. The consequences of the radiatively corrected MSSM Higgs sector are briefly discussed.