GRAND UNIFICATION FOR MIRROR FERMIONS

The possibility of grand unification of the standard model (SM) with f ermion spectrum extended to include mirror fermions is examined. SM ga uge couplings do not automatically unify. SO(10) grand unification is studied with one intermediate scale. Renormalization group equations ( RGE) for fermion Yukawa couplings and the scalar self-coupling are stu died numerically at one and two loop level. Strong restrictions for mi rror fermion masses are obtained assuming perturbative unification. Mi rror masses much smaller than the tree unitarity bounds are required. In particular mirror leptons have to be around 50 GeV. Consistency of the mirror fermion model with LEP precision data is established. A dir ect search for single production of mirror neutrinos at LEP could excl ude or confirm the GUT version of the mirror fermion model.