Neutrino Mass Origin and Flavored-QCD axion in an Extra-Dimension (2408.10632v1)

Abstract: We propose a unified flavor model with the Standard Model fields on two 3-branes within an extra-dimensional setup, incorporating $\Gamma_N\times U(1)_X$ symmetry with a modulus and scalar field responsible for symmetry breaking. When compactified to four dimensions, Yukawa couplings, initially expressed as modular forms with mass dimensions, are normalized to conform to canonical four-dimensional theory, with the Yukawa coefficients being complex numbers of unit absolute value. We show that this model naturally explains the mass and mixing hierarchies of quarks and leptons, solves the strong CP problem, provides a natural solution to the hierarchy problem, and can inherently satisfy no axionic domain-wall problem. The $U(1)_X$ mixed gravitational anomaly-free condition necessitates that electrically neutral mirror bulk fermions couple to the normal neutrino field on the 3-brane, consistent with the boundary condition. Consequently, we demonstrate a mechanism for generating light neutrino masses, similar to the Weinberg operator, by transmitting the information of $U(1)_X$ breakdown between the two 3-branes. The scale of $U(1)_X$ breaking is estimated from neutrino data to be around $10^{15}$ GeV, leading to a QCD axion mass of approximately $2.5\times10^{-9}$ eV. Through numerical analysis, we demonstrate that the model yields results consistent with current experimental data on quarks and leptons, and it also provides predictions for neutrinos.