Hiding neutrinoless double beta decay in the minimal seesaw mechanism

TL;DR

This paper explores how the minimal seesaw mechanism with hierarchical right-handed neutrinos can suppress or hide neutrinoless double beta decay through destructive interference, depending on specific mixing conditions.

Contribution

It demonstrates that in the minimal seesaw model, the lighter right-handed neutrino can significantly suppress neutrinoless double beta decay under certain mixing conditions, revealing a new potential hiding mechanism.

Findings

The lighter right-handed neutrino can suppress the decay signal.

The flavor structure of mixing depends on the Majorana CP phase.

Suppression can be complete or partial depending on parameters.

Abstract

We present a possibility that the neutrinoless double beta decay can be hidden in the minimal seesaw mechanism where the standard model is extended by two right-handed neutrinos which have a hierarchical mass structure. In this framework, the lepton number is violated due to the massive Majorana neutrinos. Especially, we investigate the case that the heavier right-handed neutrino is sufficiently heavy to decouple from the decay while the lighter one is lighter enough than the typical Fermi-momentum scale of nuclei and gives a sizable contribution to the decay. Under the specific condition on mixing elements, the lighter right-handed neutrino can give a significant destructive contribution which suppresses or even hides to the effective mass of the neutrinoless double beta decay. In this case, the flavor structure of the mixing element of the lighter right-handed neutrino with ordinary neutrinos is predicted depending on the Majorana CP violating phase of active neutrinos.