Leptogenesis in Theories with Large Extra Dimensions

TL;DR

This paper explores how leptogenesis can occur in theories with large extra dimensions, where a tower of Majorana neutrino excitations creates CP violation leading to the universe's matter-antimatter asymmetry.

Contribution

It introduces a novel leptogenesis mechanism involving Kaluza-Klein Majorana neutrinos in higher-dimensional theories, highlighting conditions for CP violation and baryogenesis.

Findings

Heavy Majorana excitations produce leptonic asymmetry

Constructive interference of Kaluza-Klein modes enhances CP violation

Reheat temperature above 5 GeV is sufficient for baryogenesis

Abstract

We study the scenario of baryogenesis through leptogenesis in higher-dimensional theories, in which the scale of quantum gravity is many orders of magnitude smaller than the usual Planck mass. The minimal realization of these theories includes an isosinglet neutrino which feels the presence of large compact dimensions, whereas all the SM particles are localized on a $(1+3)$-dimensional subspace. In the formulation of minimal leptogenesis models, we pay particular attention to the existence of Majorana spinors in higher dimensions. After compactification of the extra dimensions, we obtain a tower of Majorana Kaluza-Klein excitations which act as an infinite series of CP-violating resonators, and derive the necessary conditions for their constructive interference. Based on this CP-violating mechanism, we find that the decays of the heavy Majorana excitations can produce a leptonic asymmetry which is reprocessed into the observed baryonic asymmetry of the Universe by means of out-of-equilibrium sphaleron interactions, provided the reheat temperature is above 5 GeV.