# Dirac neutrinos in a $SU(2)$ left-right symmetric model

## TL;DR

This paper explores a left-right symmetric model where neutrinos are naturally Dirac particles, and discusses how adding a third bi-doublet can eliminate fine-tuning issues in neutrino mass generation.

## Contribution

It introduces a model with three bi-doublets and two doublets, showing how neutrinos remain Dirac fermions without fine-tuning, and considers an inert scalar doublet protected by symmetry.

## Key findings

- Neutrinos are Dirac fermions at all orders in perturbation theory.
- Adding a third bi-doublet removes the need for fine-tuning in neutrino mass.
- An inert scalar doublet can be incorporated, protected by the symmetry.

## Abstract

In a left-right symmetric model, with the scalar sector consisting of several bi-doublets and two doublets, neutrinos remain as Dirac fermions in all order in perturbation theory. Although with only two bi-doublets the neutrino masses need still a fine tuning, this is not the case when a third bi-doublet is added. One of the scalar doublet may be of the inert type since it is protected by the left-right symmetry.