Indian Journal of Science and Technology

Abstract

Background/Objectives: We will study the effects of non-unitarity parameters from existing experimental constraints, on cLFV decays such as, μ →eγ, μ →τγ, τ →eγ, on generation of baryon asymmetry through leptogenesis and neutrino oscillation probabilities. Considering flavor effects in leptogenesis, we do a parameter scan of a minimal seesaw model in a type I Seesaw framework satisfying Planck data on baryon to photon ratio of the Universe, which lies in the interval, 5.8×10^− 10 <Y_B < 6.6×10^− 10(BBN). We predict values of lightest neutrino mass, and Dirac and Majorana CP violating phase δ_CP, α and β, for normal hierarchy and inverted hierarchy for one, two and three flavor leptogenesis regimes. It is worth mentioning that all these four quantities are unknown yet, and future experiments will be measuring them. Methods/Statistical analysis: 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 non unitarily effects. We study their effects on generation of baryon asymmetry through leptogenesis. Considering flavor effects in leptogenesis, we do a parameter scan of a minimal seesaw model in a type I Seesaw framework satisfying Planck data on baryon to photon ratio of the Universe, which lies in the interval, 5.8 × 10⁻¹⁰ < Y_B < 6.6 × 10⁻¹⁰(BBN). Findings: We predict values of lightest neutrino mass, for normal hierarchy and inverted hierarchy for two and three flavor leptogenesis regimes. It is worth mentioning that all these four quantities, lightest neutrino mass, and Dirac and Majorana CP violating phase δ_CP, α and β, are unknown yet, and future experiments will be measuring them. Novelty/Applications: Unitarity in U_PMNS matrix is not yet established, and hence it has left scope for testing non unitarity in the leptonic sector which will result in various implications of New Physics theories in predicting the values of leptonic CPV phase, δ_CP, Majorana phases, α, β and the absolute value of the neutrino masses. The interesting feature of our work is that we will evaluate the absolute value of lightest neutrino mass which is found to be consistent with the cosmological constraints on the sum of the neutrino mass bound, Σ_im_( νi ) < 0.23 eV from CMB, Planck 2015 data (CMB₁₅+ LRG+ lensing + H₀). We note that absolute value of lightest neutrino mass is also not known so far, and hence our prediction made here may be tested in future when experiments (including neutrinoless double beta decay experiments) will determine its value in future.

Keywords: Non unitarity; CP violation phase; Majorana phases; leptogenesis; Baryogenesis.