Correlation between the Charged Current Interactions of Light and Heavy Majorana Neutrinos

Abstract

The evidence for neutrino oscillations implies that three neutrino flavors (ν_e, ν_μ, ν_τ) must have different mass states (ν_1, ν_2, ν_3). The most popular idea of generating tiny masses of ν_i is to introduce three heavy Majorana neutrinos N_i (for i = 1, 2, 3) into the standard model and implement the seesaw mechanism. In this approach the neutrino mixing matrix V appearing in the charged current interactions of ν_i is not unitary, and the strength of unitarity violation of V is associated with the matrix R which describes the strength of charged current interactions of N_i. We present an explicit parametrization of the correlation between V and R in terms of nine rotation angles and nine phase angles, which can be measured or constrained in the precision neutrino oscillation experiments and by exploring possible signatures of N_i at the LHC and ILC. Two special but viable scenarios, the Type-I seesaw model with two heavy Majorana neutrinos and the Type-II seesaw model with one heavy Majorana neutrino and one Higgs triplet, are taken into account to illustrate the simplified V-R correlation. The implications of R \neq 0 on the low-energy neutrino phenomenology are also discussed. In particular, we demonstrate that the non-unitarity of V is possible to give rise to an appreciable CP-violating asymmetry between ν_μ-> ν_τand \barν_μ-> \barν_τoscillations with short or medium baselines.