Phenomenology of Vanishing Effective Majorana Mass with a Sterile Neutrino under Cosmological and JUNO Constraints

TL;DR

This paper studies how a sterile neutrino can cause the effective Majorana mass to vanish in neutrinoless double beta decay within cosmological and JUNO constraints, revealing parameter space restrictions and cancellation effects.

Contribution

It identifies the parameter space where active-sterile interference leads to vanishing $M_{ee}$ and analyzes the impact of latest cosmological and JUNO data on sterile neutrino parameters.

Findings

Bounds restrict sterile mixing angle $ heta_{14}$ and lightest neutrino mass.

Cancellations driven by CP phases can nullify $|M_{ee}|$ despite JUNO constraints.

Sterile neutrino parameters may be insensitive to JUNO precision measurements.

Abstract

In the present work we investigate the phenomenological implications of a vanishing effective Majorana neutrino mass within a $3+1$ neutrino framework adding a eV-scale sterile neutrino beside three active neutrino states in light of latest cosmology driven bounds on sum of neutrino masses ($\sum_{i}m_i$). We explore the parameter space where the destructive interference between active and sterile states leads to vanishing amplitude, $M_{ee}$, of neutrinoless double beta ($0\nu\beta\beta$) decay. The allowed parameter space has been identified and predictions have been obtained taking into account the latest Planck and DESI+CMB bound on $\sum_{i}m_i$. We find that these bounds restrict the sterile mixing angle $\theta_{14}$ and the lightest active neutrino mass. Furthermore, we incorporate the refined precision data from JUNO experiment regarding solar oscillation parameters ($\theta_{12}, \Delta m_{21}^2$). We find that the sterile neutrino parameters like $\theta_{14}$ may not be sensitive to the JUNO precision measurements as the constraint imposed by precise $\theta_{12}$ is washed out by new cancellations driven through additional CP violating phases leading to vanishing $|M_{ee}|$.