Flavour physics without flavour symmetries

TL;DR

This paper presents a detailed analysis of a six-dimensional supersymmetric GUT model that predicts neutrino masses and successfully incorporates thermal leptogenesis without relying on flavour symmetries.

Contribution

It introduces a novel flavour model derived from higher-dimensional theory with specific flux compactification, predicting neutrino masses and leptogenesis without flavour symmetries.

Findings

Predicts light neutrino mass scale around 10^{-3} eV.

Estimates heavy Majorana neutrino masses between 10^{12} and 10^{14} GeV.

Successfully incorporates thermal leptogenesis.

Abstract

We quantitatively analyze a quark-lepton flavour model derived from a six-dimensional supersymmetric theory with $SO(10)\times U(1)$ gauge symmetry, compactified on an orbifold with magnetic flux. Two bulk $\mathbf{16}$-plets charged under the $U(1)$ provide the three quark-lepton generations whereas two uncharged $\mathbf{10}$-plets yield two Higgs doublets. At the orbifold fixed points mass matrices are generated with rank one or two. Moreover, the zero modes mix with heavy vectorlike split multiplets. The model possesses no flavour symmetries. Nevertheless, there exist a number of relations between Yukawa couplings, remnants of the underlying GUT symmetry and the wave function profiles of the zero modes, which lead to a prediction of the light neutrino mass scale, $m_{\nu_1} \sim 10^{-3}$ eV and heavy Majorana neutrino masses in the range from $10^{12}$ GeV to $10^{14}$ GeV. The model successfully includes thermal leptogenesis.