# Neutrinoless double beta decay in minimal left-right symmetric model with universal seesaw

## TL;DR

This paper investigates neutrinoless double beta decay within left-right symmetric models with universal seesaw, analyzing new physics contributions, parameter constraints, and compatibility with experimental and cosmological bounds.

## Contribution

It provides a detailed analysis of $0
u eta eta$ decay in minimal left-right symmetric models with universal seesaw, highlighting the role of light right-handed neutrinos and their impact on decay rates.

## Key findings

- Light right-handed neutrinos can be as light as a few keV.
- Heavy-light neutrino mixing diagrams can saturate experimental bounds.
- Parameter space remains consistent with charged lepton flavor violation and cosmological constraints.

## Abstract

We present a detailed discussion on neutrinoless double beta decay $(0\nu \beta \beta)$ within left-right symmetric models based on the gauge symmetry of type $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ as well as $SU(3)_L \times SU(3)_R \times U(1)_{X}$ where fermion masses including that of neutrinos are generated through a universal seesaw mechanism. We find that one or more of the right-handed neutrinos could be as light as a few keV if left-right symmetry breaking occurs in the range of a few TeV to 100 TeV. With such light right-handed neutrinos, we perform a detailed study of new physics contributions to $0\nu \beta \beta$ and constrain the model parameters from the latest experimental bound on such a rare decay process. We find that the new physics contribution to $0\nu \beta \beta$ in such a scenario, particularly the heavy-light neutrino mixing diagrams, can individually saturate the existing experimental bounds, but their contributions to total $0\nu \beta \beta$ half-life cancels each other due to unitarity of the total $6\times 6$ mass matrix. The effective contribution to half-life therefore, arises from the purely left and purely right neutrino and gauge boson mediated diagrams. We find that the parameter space saturating the $0\nu \beta \beta$ bounds remain allowed from the latest experimental bounds on charged lepton flavour violating decays like $\mu \rightarrow e \gamma$. We finally include the bounds from cosmology and supernova to constrain the parameter space of the model.