Flavor puzzle in three Higgs-doublet models: Insights from BGL and lessons from flavor data

TL;DR

This paper investigates a specific three-Higgs-doublet model with a unique symmetry that suppresses certain flavor-changing processes, offering new insights into flavor physics and Higgs interactions.

Contribution

It introduces the BGL-3HDM with a $U(1)_1\times U(1)_2$ symmetry, reducing free parameters while allowing flavor nonuniversality in Higgs couplings.

Findings

FCNCs are confined to the up-quark sector.

The model is as economical as NFC models in terms of parameters.

Flavor nonuniversality arises despite diagonal Yukawa matrices.

Abstract

We study a variant of the 3HDM, referred to as the BGL-3HDM, incorporating a $U(1)_1\times U(1)_2$ symmetry, which can distinguish the primary sources of mass for different fermion generations. In the version considered here, the Yukawa matrices in the down-quark and charged lepton sectors are diagonal, thereby eliminating tree-level FCNCs in these sectors. FCNC interactions mediated by neutral nonstandard Higgses are confined to the up-quark sector only. No new BSM parameters are introduced by the Yukawa sector of the model, making it as economical as the NFC versions of 3HDM with a $U(1)_1\times U(1)_2$ symmetry in terms of the number of free parameters. However, even in the down-quark and in the charged lepton sectors, flavor diagonal but nonuniversal Higgs couplings set this model apart from the NFC versions of the 3HDM.