Active Dirac Neutrinos via $SU(2)_L$ Doublets in 5d

TL;DR

This paper introduces a novel five-dimensional mechanism for generating tiny active neutrino masses without singlet neutrinos, utilizing boundary conditions and bulk mass terms in an interval spacetime.

Contribution

It presents a new approach to neutrino mass generation in 5d models, avoiding the need for $SU(2)_L$ singlet neutrinos and employing boundary conditions and bulk masses.

Findings

A bulk mass in 5d can produce a tiny Dirac neutrino mass.

The mechanism is compatible with the standard model when gauge bosons and Higgs are localized.

Provides a new tool for constructing neutrino mass models.

Abstract

We propose a new mechanism to generate minuscule active neutrino masses in a five-dimensional~(5d) spacetime of an interval without introducing $SU(2)_L$ singlet neutrinos. Under asymmetric boundary conditions on the two end points, a bulk mass for a 5d fermion allows a Dirac particle with a tiny mass eigenvalue. Implementing this mechanism, which provides us a new tool for building neutrino mass models, to the standard model gauge structure is possible when all the gauge bosons and the Higgs boson are localized on one of the branes.