Lepton mixing from the hidden sector

TL;DR

This paper proposes a theoretical framework combining the double seesaw mechanism, SO(10) GUT, and a hidden sector with specific symmetries to explain the observed relation between lepton and quark mixing matrices.

Contribution

It introduces a novel model that links the lepton and quark mixing matrices through hidden sector symmetries and basis-fixing mechanisms within a grand unified theory context.

Findings

Framework can produce the relation U_PMNS ≈ V_CKM^\u2026 U_X.

Identifies basis-fixing symmetry Z2 x Z2 as key to flavor structure.

Provides minimal realizations with different mediators and symmetries.

Abstract

Experimental results indicate a possible relation between the lepton and quark mixing matrices of the form U_PMNS \approx V_CKM^\dagger U_X, where U_X is a matrix with special structure related to the mechanism of neutrino mass generation. We propose a framework which can realize such a relation. The main ingredients of the framework are the double seesaw mechanism, SO(10) Grand Unification and a hidden sector of theory. The latter is composed of singlets (fermions and bosons) of the GUT symmetry with masses between the GUT and Planck scale. The interactions in this sector obey certain symmetries G_hidden. We explore the conditions under which symmetries G_hidden can produce flavour structures in the visible sector. Here the key elements are the basis-fixing symmetry and mediators which communicate information about properties of the hidden sector to the visible one. The interplay of SO(10) symmetry, basis-fixing symmetry identified as Z2 x Z2 and G_hidden can lead to the required form of U_X. A different kind of new physics is responsible for generation of the CKM mixing. We present the simplest realizations of the framework which differ by nature of the mediators and by symmetries of the hidden sector.