Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.36060

Hybrid seesaw from $SU(2)_1 \times SU(2)_2 \times U(1)_Y$

Antonio Herrero-Brocal·Javier Perez-Soler·Avelino Vicente
View original source ↗Read source document ↗Export metadata ↓

Abstract

We study neutrino mass generation in a model based on the $SU(3)_c \times SU(2)_1 \times SU(2)_2 \times U(1)_Y$ gauge symmetry, in which the Standard Model $SU(2)_L$ arises at low energies as the diagonal subgroup of the two $SU(2)$ factors. The symmetry is enlarged with a global $U(1)_{B-L}$ symmetry, spontaneously broken by the vacuum expectation value of a scalar bidoublet. Light neutrino masses are generated at tree level through a hybrid of the type-III, inverse and linear seesaw mechanisms. A distinctive feature of the construction is the existence of a Nambu-Goldstone boson, the majoron, which transforms non-trivially under the original gauge symmetry while being mostly singlet under the Standard Model gauge group. We explore the phenomenological consequences of this setup, including electroweak precision constraints, the production of the nearly degenerate $W'$ and $Z'$ bosons at colliders and lepton flavor violating decays with a majoron in the final state. The latter constitute the most promising signature of the model.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Antonio Herrero-Brocal, Javier Perez-Soler, Avelino Vicente. 2026-10-26. Hybrid seesaw from $SU(2)_1 \times SU(2)_2 \times U(1)_Y$. https://arxiv.org/abs/2610.36060

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Background-Induced Forces from Quadratically Coupled Ultralight Dark Matter

Quadratically coupled ultralight scalar dark matter behaves as a coherent classical field whose interactions with matter can induce a composition-dependent force through the dark matter background. We present a complete calculation of this background-induced force beyond the spherically symmetric approximation. Using a partial-wave treatment of dark-matter scattering, we determine its angular dependence and derive an analytic description valid even when the dark-matter wavelength is much smaller than the Earth's radius. We show for the first time that Earth screening generates a characteristic frequency-band structure, splitting the signal into multiple sidebands that provide a distinctive experimental signature. We further show that the relative amplitudes of these sidebands vary annually as the satellite's Sun-synchronous orbital plane precesses in step with the Earth's revolution around the Sun, allowing us to construct a complete signal template. As an application of these results, we re-evaluate constraints from the MICROSCOPE mission, which currently provides the strongest laboratory limits on equivalence-principle violations from ultralight dark matter. We further show that proposed space-based equivalence-principle experiments, such as Galileo Galilei and STE-QUEST, can significantly enhance their sensitivity to ultralight scalar dark matter by incorporating the full frequency-band information.

hep-ph↗
arXiv2026

Universal seesaw mechanism for fermion masses and strong CP problem

We propose a framework for fermion mass generation based on a universal seesaw. The Standard Model is extended by an Abelian gauge symmetry acting on right-handed fermions, together with vector-like fermions and scalar fields. The ordinary Yukawa couplings are forbidden, except for the top-quark coupling to the Higgs, which is allowed at the renormalizable level and remains unsuppressed. The charged-fermion hierarchies then arise from mixing with the vector-like sector, and light neutrino masses emerge from a neutral sector Majorana seesaw. CP is exact in the ultraviolet and broken spontaneously by scalar vacuum expectation values. The resulting CP-violating phase is transmitted to the quark sector and generates the CKM phase, while a Nelson-Barr structure, realized through the universal seesaw block form, keeps the physical QCD vacuum angle zero at tree level. Consistency with EDM bounds beyond tree level requires moderately suppressed Yukawa couplings between SM doublets to the vector-like sector. If the leading higher-dimensional operators are unsuppressed, the same requirement can favor a low breaking scale for the new Abelian symmetry. In this regime the vector-like fermions can lie at the TeV scale, with suppressed mixing with the electroweak sector. This framework provides a simple setting in which the hierarchies of charged-fermion masses, neutrino masses, and CP-violating parameters can be accounted for within a common extension of the Standard Model.

hep-ph↗
arXiv2026

Precise bubble wall velocity in a specific phase transition pattern in the CxSM and beyond

The bubble wall velocity is a key quantity in cosmological first-order phase transitions, with important implications for electroweak baryogenesis, gravitational wave signals, the dark matter relic density and primordial black holes formed during the phase transition. However, it is often treated as a free input in phenomenological studies, while a self-consistent determination remains challenging. In this work, taking the complex singlet extension of the Standard Model as an example, we investigate the bubble wall dynamics and velocity in a specific electroweak phase transition pattern where both the Higgs field and the coupled singlet scalar experience friction. The microscopic friction arising from particle interactions with the plasma is evaluated using Boltzmann transport equations, while the macroscopic plasma response is described through hydrodynamic analysis. By applying the steady state force balance condition, we numerically determine the bubble wall velocity for different model parameters. We show that the wall velocity is governed by the competition between the driving force from the effective potential and plasma friction, and that its variation can significantly affect the baryon asymmetry. Our study provides a quantitative investigation of bubble wall dynamics in this overlooked phase transition pattern and its implications for early Universe phenomenology.

hep-ph↗