Running Effects on Lepton Mixing Angles in Flavour Models with Type I Seesaw

TL;DR

This paper investigates how renormalization group effects influence lepton mixing angles in type I seesaw models with flavor symmetries, finding stability in normal hierarchy but potential deviations in inverted hierarchy.

Contribution

It provides a detailed analysis of RG running effects on tribimaximal mixing in flavor models, highlighting the dominant role of charged lepton contributions and stability in normal hierarchy.

Findings

Mixing angles are stable in normal hierarchy.

Inverted hierarchy can lead to significant deviations.

Charged lepton sector primarily drives RG effects.

Abstract

We study renormalization group running effects on neutrino mixing patterns when a (type I) seesaw model is implemented by suitable flavour symmetries. We are particularly interested in mass-independent mixing patterns to which the widely studied tribimaximal mixing pattern belongs. In this class of flavour models, the running contribution from neutrino Yukawa coupling, which is generally dominant at energies above the seesaw threshold, can be absorbed by a small shift on neutrino mass eigenvalues leaving mixing angles unchanged. Consequently, in the whole running energy range, the change in mixing angles is due to the contribution coming from charged lepton sector. Subsequently, we analyze in detail these effects in an explicit flavour model for tribimaximal neutrino mixing based on an A4 discrete symmetry group. We find that for normally ordered light neutrinos, the tribimaximal prediction is essentially stable under renormalization group evolution. On the other hand, in the case of inverted hierarchy, the deviation of the solar angle from its TB value can be large depending on mass degeneracy.