Effects of Leptonic Nonunitarity on Lepton Flavor Violation, Neutrino Oscillation, Leptogenesis, and Lightest Neutrino Mass

Abstract

Neutrino physics is a mature branch of science with all the three neutrino mixing angles and two mass squared differences determined with high precision. In spite of several experimental verifications of neutrino oscillations and precise measurements of two mass squared differences and the three mixing angles, the unitarity of the leptonic mixing matrix is not yet established, leaving room for the presence of small nonunitarity effects. Deriving the bounds on these nonunitarity parameters from existing experimental constraints, on cLFV decays such as $\mu \to e\gamma$, $\mu \to \tau \gamma$, and $\tau \to e\gamma$, we study their effects on the generation of baryon asymmetry through leptogenesis and neutrino oscillation probabilities. We consider a model where see-saw is extended by an additional singlet $S$ which is very light but can give rise to nonunitarity effects without affecting the form on see-saw formula. We do a parameter scan of a minimal see-saw model in a type I see-saw framework satisfying the Planck data on baryon to photon ratio of the Universe, which lies in the interval $\mathrm{5.8}\times \mathrm{1}{\mathrm{0}}^{-\mathrm{10}}<Y_B<\mathrm{6.6}\times \mathrm{1}{\mathrm{0}}^{-\mathrm{10}}(BBN)$. We predict values of lightest neutrino mass and Dirac and Majorana CP-violating phases ${\delta }_{CP}$, $\alpha$, and $\beta$, for normal hierarchy and inverted hierarchy for one-flavor leptogenesis. It is worth mentioning that all these four quantities are unknown yet, and future experiments will be measuring them.