The Cabibbo Angle in a Supersymmetric D14 Model

TL;DR

This paper presents a supersymmetric flavor model based on D14 symmetry that naturally predicts the Cabibbo angle close to experimental values by leveraging specific subgroup conservation and flavon-induced symmetry breaking.

Contribution

The model introduces a novel D14 flavor symmetry combined with Z3 and Froggatt-Nielsen mechanisms to accurately reproduce quark mixing angles and mass hierarchies.

Findings

Predicts |V_{ud}| = cos(pi/14) with high precision

Achieves realistic quark mass hierarchies through symmetry breaking

Results remain stable under small perturbations of flavon vacuum alignment

Abstract

We construct a supersymmetric model with the flavor symmetry D14 in which the CKM matrix element |V_{ud}| can take the value |V_{ud}| =cos (pi/14) = 0.97493 implying that the Cabibbo angle theta_C is sin (theta_C) = |V_{us}| = sin (pi/14) = 0.2225. These values are very close to those observed in experiments. The value of |V_{ud}| (theta_C) is based on the fact that different Z2 subgroups of D14 are conserved in the up and down quark sector. In order to achieve this, D14 is accompanied by a Z3 symmetry. The spontaneous breaking of D14 is induced by flavons, which are scalar gauge singlets. The quark mass hierarchy is partly due to the flavor group D14 and partly due to a Froggatt-Nielsen symmetry U(1)_{FN} under which only the right-handed quarks transform. The model is completely natural in the sense that the hierarchies among the quark masses and mixing angles are generated with the help of symmetries. The issue of the vacuum alignment of the flavons is solved up to a small number of degeneracies, leaving four different possible values for |V_{ud}|. Out of these, only one of them leads to a phenomenological viable model. A study of the Z2 subgroup breaking terms shows that the results achieved in the symmetry limit are only slightly perturbed. At the same time they allow |V_{ud}| (theta_C) to be well inside the small experimental error bars.