Zhiqing ZHANG

Introduction Supersymmetry (SUSY) is one of the most likely ingredients for a theory beyond the Standard Model (SM). In particular the Minimal Supersymmetric extension of the Standard Model (MSSM) describes as well as the SM all experimental data, and in addition it offers among its appealing consequences solutions for the cancellation of quadratic divergences occurring in the scalar Higgs sector of the SM and models beyond the SM. SUSY relates fermions to bosons and predicts for each SM particle a partner with spin differing by half a unit. For example selectrons ~ e L , ~ e R are scalar partners of electrons e L , e R , and similarly squarks (~u L ; ~ dL ), ~ uR , ~ dR are the partners of up and down quarks. Two Higgs doublets with vacuum expectation values v 2<F53.8