Warped Seesaw is Physically Inverted

TL;DR

This paper reveals that in warped extra-dimensional models, neutrino masses are generated via a mechanism akin to the inverse seesaw, linking TeV-scale physics with neutrino mass and leptogenesis, differing from the traditional type I seesaw.

Contribution

It demonstrates that warped 5D models naturally realize an inverse seesaw mechanism for neutrino mass generation, contrasting with the conventional type I seesaw.

Findings

Neutrino masses are dominated by TeV-scale singlet states.

The mechanism resembles an inverse seesaw rather than a type I seesaw.

Dual CFT analysis supports the 5D results.

Abstract

Warped extra dimensions can address both the Planck-weak and flavor hierarchies of the Standard Model (SM). In this paper we discuss the SM neutrino mass generation in a scenario in which a SM singlet bulk fermion - coupled to the Higgs and the lepton doublet near the IR brane - is given a Majorana mass of order the Planck scale on the UV brane. Despite the resemblance to a type I seesaw mechanism, a careful investigation based on the mass basis for the singlet 4D modes reveals a very different picture. Namely, the SM neutrino masses are generated dominantly by the exchange of the TeV-scale mass eigenstates of the singlet, that are pseudo-Dirac and have a sizable Higgs- induced mixing with the SM doublet neutrino: remarkably, in warped 5D models the anticipated type I seesaw morphs into a natural realization of the so-called "inverse" seesaw. This understanding uncovers an intriguing and direct link between neutrino mass generation (and possibly leptogenesis) and TeV-scale physics. We also perform estimates using the dual CFT picture of our framework, which back-up our 5D calculation.