Flavored $S_3$ Non-Minimal Left-Right Symmetric Model

Abstract

In this work we investigate fermion masses and flavor mixings in a non-minimal left-right symmetric model endowed with the non-Abelian discrete symmetry $S_3$. The scalar sector contains three Higgs bidoublets, while one left-handed and one right-handed triplet generate Majorana neutrino masses. Assigning the first two fermion families to an $S_3$ doublet and the third family to a singlet, together with a specific alignment of the bidoublet vacuum expectation values, leads to a common and analytically tractable structure for the fermion mass matrices. We study both the pseudomanifest and manifest left-right realizations, in which the fermion mass matrices are complex symmetric and Hermitian, respectively, and derive analytical expressions for the left- and right-handed CKM and PMNS mixing matrices. A numerical likelihood test shows that the model successfully reproduces the observed quark and lepton mixing patterns for both normal and inverted neutrino mass orderings at the level of oscillation data. Remarkably, the manifest scenario emerges as a more restrictive realization of the pseudomanifest one, with the main distinction residing in their CP-phase structure. We further explore the phenomenological consequences for the neutrinoless double-beta decay, the muon anomalous magnetic moment, and the lepton-flavor-violating decay $\mu \to e\gamma$. The right-handed contribution exhibits the characteristic dependence on the heavy-neutrino and $W_R$ mass scales, while flavor corrections are found to be subleading over most of the allowed parameter space. These results show that an $S_3$ flavor symmetry can simultaneously organize fermion mixing and lead to distinctive low-energy signatures within left-right symmetric theories.

arXiv comment31 pages, 10 figures