Warped Leptogenesis with Dirac Neutrino Masses

TL;DR

This paper proposes a novel TeV-scale leptogenesis mechanism using warped extra dimensions, where tiny Majorana mass contributions induce small neutrino mass splittings, enabling sufficient CP asymmetry for baryogenesis.

Contribution

It introduces a warped extra-dimensional model where Dirac neutrinos with negligible Majorana masses can generate baryon asymmetry at the TeV scale through small mass splittings of Kaluza-Klein states.

Findings

Leptogenesis can occur at TeV scale with warped extra dimensions.

Tiny Majorana mass terms induce small neutrino mass splittings.

Sufficient CP asymmetry achieved without high mass scales.

Abstract

We show how leptogenesis can occur at the TeV scale with neutrinos that possess almost purely Dirac masses and negligible Majorana mass contributions as a consequence of the small wavefunction overlap in a warped fifth dimension. Lepton number violation at the Planck scale is introduced via a Majorana mass term on the Planck brane. Such a Majorana mass operator leads to the small mass splitting of otherwise degenerate Kaluza-Klein excited states on the TeV brane. This tiny mass splitting can compensate for the small Yukawa couplings to give a CP asymmetry large enough to produce the sufficient baryon asymmetry from the decay of the nearly degenerate neutrino Kaluza-Klein states. In this way the standard baryogenesis via leptogenesis scenario can naturally occur at the TeV scale without the need for a high mass scale.