Lepton Flavour Violation in the Minimal SO(10) GUT Model and in the Standard Model with additional Heavy Dirac Neutrinos

Lepton flavour violation is considered in two models, Standard Model with additional heavy Dirac neutrinos and minimal supersymmetric standard model (MSSM) with SO(10) theoretical frame and minimal SUGRA (mSUGRA) SUSY-breaking mediation mechanism. The models are briefly explained. The structure of the amplitudes for neutrinoless decays of the lepton into a lepton and semileptonic neutrinoless decays of a lepton is given. The method for identification of meson content in the quark currents is exposed. The comparison of the amplitudes is made showing which of the processes have the largest branching ratios. The numerical results for the dominant decay rates are presented.