Leptogenesis within a generalized quark-lepton symmetry

TL;DR

This paper explores a relaxed quark-lepton symmetry in neutrino mass models, demonstrating that certain hierarchical structures can produce successful leptogenesis and neutrino phenomenology at an intermediate mass scale.

Contribution

It introduces a generalized hierarchical quark-lepton symmetry allowing for viable leptogenesis within see-saw models by relaxing strict symmetry conditions.

Findings

Hierarchical Dirac mass matrices compatible with neutrino data

Off-diagonal heavy Majorana mass matrices support leptogenesis

Successful baryogenesis at an intermediate scale ~10^{12} GeV

Abstract

Quark-lepton symmetry has been shown to be inconsistent with baryogenesis via leptogenesis in natural schemes of the see-saw mechanism. Within the phenomenological approach of textures, we relax this strict symmetry and propose weaker conditions, namely models of the neutrino Dirac mass matrix $M_D$ which have the same hierarchy as the matrix elements of $M_u$. We call this guide-line generalized $hierarchical$ quark-lepton symmetry. We consider in detail particular cases in which the moduli of the matrix elements of $M_D$ are equal to those of $M_u$. Within the phenomenological approach of textures, we try for the heavy Majorana mass matrix diagonal and off-diagonal forms. We find that an ansatz for $M_D$ preserving the hierarchy, together with an off-diagonal model for the heavy Majorana neutrino mass, is consistent with neutrino masses, neutrino mixing and baryogenesis via leptogenesis for an intermediate mass scale $m_R \sim 10^{12}$ GeV. The preservation of the hierarchical structure could come from a possible symmetry scheme.