Connecting Neutrino Masses and Dark Matter by High-dimensional Lepton Number Violation Operator

TL;DR

This paper introduces a two-loop neutrino mass model linked to dark matter, driven by a dimension-7 lepton number violation operator, with implications for neutrinoless double beta decay and dark matter phenomenology.

Contribution

It presents a novel two-loop neutrino mass generation mechanism using a dimension-7 operator, ensuring dark matter stability and predicting a normal hierarchy for neutrino masses.

Findings

Neutrino masses follow a normal hierarchy.

The model predicts observable lepton flavor violation signals.

Dark matter candidate is stable and consistent with relic abundance.

Abstract

We propose a new model with the Majorana neutrino masses generated at two-loop level, in which the lepton number violation (LNV) processes, such as neutrinoless double beta decays, are mainly induced by the dimension-7 LNV effective operator O_7=\bar l_R^c \gamma^\mu L_L(D_mu \Phi) \Phi \Phi. Note that it is necessary to impose an Z_2 symmetry in order that O_7 dominates over the conventional dimension-5 Weinberg operator, which naturally results in a stable Z_2-odd neutral particle to be the cold dark matter candidate. More interestingly, due to the non-trivial dependence of the charged lepton masses, the model predicts the neutrino mass matrix to be in the form of the normal hierarchy. We also focus on a specific parameter region of great phenomenological interests, such as electroweak precision tests, dark matter direct searches along with its relic abundance, and lepton flavor violation processes.