Effects Of leptonic non-unitarity on lepton flavor violation, neutrino oscillation, leptogenesis and lightest neutrino mass

TL;DR

This paper investigates how small non-unitarity effects in the leptonic mixing matrix influence lepton flavor violation, neutrino oscillations, and leptogenesis, using a model extended with a light singlet to satisfy cosmological constraints.

Contribution

It introduces a model extending the type I see-saw with a light singlet to study non-unitarity effects without altering the see-saw structure, and performs a parameter scan consistent with cosmological data.

Findings

Bounds on non-unitarity parameters from cLFV decays are derived.

Predictions for the lightest neutrino mass and CP phases are made for different hierarchies.

The model satisfies the Planck data on baryon asymmetry of the Universe.

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. Inspite 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 non-unitarity effects. Deriving the bounds on these non-unitarity parameters from existing experimental constraints, on cLFV decays such as, $ \mu\rightarrow e\gamma $, $ \mu\rightarrow \tau\gamma $, $ \tau\rightarrow 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 non-unitarity 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, $5.8\times 10^ {-10} < Y _{B} < 6.6 \times 10^ {-10} (BBN)$. We predict values of lightest neutrino mass, and Dirac and Majorana CP-violating phase $ \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.