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

TL;DR

This paper explores the relationship between light and heavy Majorana neutrinos' charged current interactions, providing a parametrization that links observable neutrino oscillation effects to heavy neutrino signatures at colliders.

Contribution

It introduces an explicit parametrization of the correlation between the neutrino mixing matrix and heavy neutrino interactions, applicable to various seesaw models and experimental scenarios.

Findings

Non-unitarity of the neutrino mixing matrix can cause observable CP violation.

The parametrization can be tested in neutrino oscillation experiments and collider searches.

Implications for low-energy neutrino phenomenology are discussed.

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.