Neutrino mass models and RGE contribution to LFV leptonic decays

Abstract

In the first part of this thesis, we construct two viable extensions of the SM with a heavy vector in the fundamental SU (2)L representation and nine SM singlet scalar fields, consistent with the current SM fermion mass spectrum and fermionic mixing parameters. The small masses for the active neutrinos are generated from radiative seesaw mechanism at one loop level mediated by the neutral components of the heavy vector as well as by the left handed Majorana neutrinos. The proposed models predicts rates for charged lepton flavor violating processes within the reach of the forthcoming experiments. In the second part, we consider the lepton-flavor violating (LFV) lepton-quark dimension-6 operators and analyze their contributions to the LFV leptonic decays of vector, pseudoscalar, and scalar neutral mesons M → ℓ1ℓ2 as well as to µ(τ ) → ℓee, ℓγγ decays. These operators contribute to the purely leptonic processes via quark loop. On the basis of quark-hadron duality, we relate these loops to the appropriate meson-exchange contributions. In this way, we extract lower bounds on the individual scales of the studied LFV operators from the experimental and phenomenological limits on the leptonic decays of mesons and leptons. As a byproduct, we shall obtain new limits on the LFV leptonic decays of flavored mesons from the experimental bounds on the three-body lepton decays. We study the effects of QED and QCD radiative corrections to the LFV lepton-quark operators in question. We derive for them the one-loop matrix of the RGE evolution and examine its effect on the previously derived tree-level limits on these operators. We show that the QED corrections are particularly relevant due to operator mixing. Specifically, for some of them the limits on their individual LFV scales improve by up to 3 orders of magnitude.