Tri-hypercharge versus tri-darkcharge

TL;DR

The paper presents a renormalizable extension of the Standard Model in which each fermion generation carries a distinct hypercharge under $U(1)_{Y_a}$, while right-handed neutrinos are charged under a dark $U(1)_ ext{D}$ that leaves a residual dark parity. This fully flipped inert doublet model yields a hybrid Type-I and radiative (scotogenic) seesaw for neutrino masses and provides a Majorana dark matter candidate stabilized by the dark parity. A flavon sector and vector-like fermions generate the observed charged-fermion mass hierarchies and suppress CKM mixing via higher-dimensional operators, with the Higgs coupling primarily giving third-generation masses at renormalizable level. The framework is extensively tested against electroweak precision data, collider bounds, flavor observables, and dark-matter constraints, and it remains viable with distinctive phenomenology such as extra neutral gauge bosons and dark-sector states. Overall, the work links the origin of neutrino masses, dark matter stability, and the fermion flavor structure within a minimal, anomaly-free, ultraviolet-complete construction, offering testable predictions for future experiments.

Abstract

We propose a minimal, ultraviolet-complete, and renormalizable extension of the Standard Model, in which the three generations of ordinary fermions are distinguished by family-dependent hypercharges, while three right-handed neutrinos are separated by a dark gauge symmetry that is trivial for all Standard Model fields. This setup yields a fully flipped inert doublet model. The model naturally realizes a hybrid scotoseesaw mechanism that accounts for the smallness of neutrino masses and the largeness of lepton mixing. Simultaneously, it explains the stability and relic abundance of dark matter through a residual dark parity and addresses the hierarchies of charged fermion masses and the suppression of quark mixing via higher-dimensional operators involving high-scale scalar singlets and vector-like fermions. We explore the phenomenological implications of the model and derive constraints from electroweak precision tests, collider searches, flavor-changing processes, and observations of dark matter.

Figures (10)

• Figure 1: Diagrams relate to the generation of up-quark masses and mixing.
• Figure 2: Scotogenic neutrino mass generation governed by residual dark parity.
• Figure 3: Correlation between the quark mixing angles and the Jarlskog invariant.
• Figure 4: Correlation among some lepton sector observables.
• Figure 5: Red, brown, pink, orange, gray, and black curves denote the exclusion bounds derived from the $\rho$ parameter ParticleDataGroup:2024cfk, $\varepsilon_{1,2}$ mixing parameters ALEPH:2005abErler:2009jh, total $\mathcal{Z}$ decay width ParticleDataGroup:2024cfk, LEPII ALEPH:2013dgf, ATLAS ATLAS:2019erb and CMS CMS:2021ctt, respectively. The shaded regions indicate the excluded parameter space. The dashed blue line corresponds to the gauge unification condition $g_1=g_2=g_3=\sqrt3 g_Y$.