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

Abstract

The evidence for neutrino oscillations implies that three neutrino flavors (\nu_e, \nu_\mu, \nu_\tau) must have different mass states (\nu_1, \nu_2, \nu_3). The most popular idea of generating tiny masses of \nu_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 \nu_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 \nu_\mu -> \nu_\tau and \bar{\nu}_\mu -> \bar{\nu}_\tau oscillations with short or medium baselines.