SUSY Phenomenology a

Supersymmetry (SUSY) is a symmetry between fermions and bosons and its theoretical development started from the formulation of SUSY invariant Lagrangian in four dimensional field theory in early ’70s. Subsequently, SUSY gauge theory, supergravity and string theory with space-time supersymmetry (supersrting) were formulated in ’70s. Phenomenological application of SUSY theory has developed since early ’80s in connection with naturalness problem in the Standard Model (SM). One interesting possibility beyond the SM is an idea that various interactions are unified at very high energy scale. Examples are grand unified theory (GUT) and string unification. In such theories the cutoff energy scale for the SM is considered to be close to the Planck scale (∼ 10 GeV) and the quadratic divergence of the Higgs field in the SM is very problematic because very precise fine tuning between the bare mass term and radiative correction is necessary to ensure that the weak scale is smaller by 10 orders than the Planck scale. In SUSY theories this problem can be avoided due to cancellation of the quadratic divergence in scaler mass renormalization. From this point of view SUSY extensions of the SM and the GUT have been extensively studied for more than 15 years. In the experimental side, the SM has been very successful. LEP and SLAC experiments at the Z pole showed quantitative agreement of various observables with SM predictions. It was also pointed out that three gauge coupling constants determined precisely there are consistent with the SUSY SU(5) GUT assumption although non-SUSY version of the simple SU(5)GUT