Lepton CP violation in a ν2HDM with flavor

Abstract

In this work we propose an extension to the Standard Model in which we consider a type-III two-Higgs-doublet model (2HDM) plus massive neutrinos and the horizontal flavor symmetry ${S}_{3}$ ($\ensuremath{\nu}2\mathrm{HDM}\ensuremath{\bigotimes}{S}_{3}$). In the above framework and with the explicit breaking of flavor symmetry ${S}_{3}$, the Yukawa matrices in the flavor-adapted basis are represented by means of a matrix with two texture zeros. Also, the active neutrinos are considered as Majorana particles and their masses are generated through the type-I seesaw mechanism. The unitary matrices that diagonalize the mass matrices, as well as the flavor-mixing matrices, are expressed in terms of fermion mass ratios. Consequently, in the mass basis the entries of the Yukawa matrices naturally acquire the form of the so-called Cheng-Sher ansatz. For the leptonic sector of $\ensuremath{\nu}2\mathrm{HDM}\ensuremath{\bigotimes}{S}_{3}$, we compare, through a ${\ensuremath{\chi}}^{2}$ likelihood test, the theoretical expressions of the flavor-mixing angles with the masses and flavor-mixing leptons current experimental data. The results obtained in this ${\ensuremath{\chi}}^{2}$ analysis are in very good agreement with the current experimental data. We also obtain allowed value ranges for the ``Dirac-like'' phase factor, as well as for the two Majorana phase factors. Furthermore, we study the phenomenological implications of these numerical values of the $CP$-violation phases on the neutrinoless double-beta decay, and for long baseline neutrino oscillation experiments such as T2K, $\mathrm{NO}\ensuremath{\nu}\mathrm{A}$, and DUNE.