Bounds on the Mass of Excited Fermions

Abstract

According to the present limits, it is possible that the mass of the excited fermions (M*), which arise in composite models of quarks and leptons, could lay in the range: mW<M*≪Λ, where Λ denotes the scale of compositeness. For this scenario, the effective Lagrangian approach should be applied to study systematically the effects of these new fermions. Using this approach, we discuss the validity of the limits on M* obtained at FNAL from the direct search. We also derive indirect bounds on M*, which are independent of Λ, from high precision measurements, using three models (sequential, mirror and homodoublet).