Search

Abstract With just the Standard Model Higgs doublet, there are only three types of seesaw models that generate light Majorana neutrino masses at tree level after electroweak spontaneous symmetry breaking. However, if there exist additional TeV scalars acquiring vacuum expectation values, coupled with heavier fermionic multiplets, several new seesaw models become possible. These new seesaws are the primary focus of this study and correspond to the tree-level ultraviolet completions of the effective operators studied in a companion publication. We are interested in the genuine cases, in which the standard seesaw contributions are absent. In addition to the tree-level generation of neutrino masses, we also consider the one-loop contributions. Furthermore, we construct low-energy versions that exhibit a very rich phenomenology. Specifically, we scrutinise the generation of dimension-6 operators and explore their implications, including non-unitarity of the leptonic mixing matrix, non-universal $$Z-$$ Z - boson interactions, and lepton flavor violation. Finally, we provide (Generalised) Scotogenic-like variants that incorporate viable dark matter candidates.

Abstract We propose a model for leptons based on the smallest modular finite group Γ2 ≅ S 3 that, for the first time, accounts for both the hints of large low-energy CP-violation in the lepton sector and the matter-antimatter asymmetry of the Universe, generated by only two heavy right-handed neutrinos. These same states are also employed in a Minimal seesaw mechanism to generate light neutrino masses. Besides the heavy neutrinos, our particle content is the same as the Standard Model (SM), with the addition of one single modulus τ, whose vacuum expectation value is responsible for both the modular and CP-symmetry breakings. We show that this minimalistic SM extension is enough to get an excellent fit to low energy neutrino observables and to the required baryon asymmetry η B . Predictions for the neutrino mass ordering, effective masses in neutrinoless double beta decay and tritium decay as well as for the Majorana phases are also provided.

Abstract The unique dimension-5 effective operator, LLHH, known as the Weinberg operator, generates tiny Majorana masses for neutrinos after electroweak spontaneous symmetry breaking. If there are new scalar multiplets that take vacuum expectation values (VEVs), they should not be far from the electroweak scale. Consequently, they may generate new dimension-5 Weinberg-like operators which in turn also contribute to Majorana neutrino masses. In this study, we consider scenarios with one or two new scalars up to quintuplet SU(2) representations. We analyse the scalar potentials, studying whether the new VEVs can be induced and therefore are naturally suppressed, as well as the potential existence of pseudo-Nambu-Goldstone bosons. Additionally, we also obtain general limits on the new scalar multiplets from direct searches at colliders, loop corrections to electroweak precision tests and the W-boson mass.

DUNE is a next-generation long-baseline neutrino oscillation experiment. It is expected to measure, with unprecedented precision, the atmospheric oscillation parameters, including the CP-violating phase δCP. Moreover, several studies have suggested that its unique features should allow DUNE to probe several new physics scenarios. In this work, we explore the performances of the DUNE far detector in constraining new physics if a high-energy neutrino flux is employed (HE-DUNE). We take into account three different scenarios: Lorentz Invariance Violation (LIV), Long-Range Forces (LRFs) and Large Extra Dimensions (LEDs). Our results show that HE-DUNE should be able to set bounds competitive to the current ones and, in particular, it can outperform the standard DUNE capabilities in constraining CPT-even LIV parameters and the compactification radius RED of the LED model.

In the absence of a Grand Unified Theory framework, connecting the values of the mixing parameters in the quark-and-lepton sector is a difficult task, unless one introduces ad hoc relations among the matrices that diagonalize such different kinds of fermions. In this paper, we discuss in detail the possibility that the PMNS matrix is given by the product UPMNS=VCKM★T★, where T comes from the diagonalization of a see-saw like mass matrix that can be of a Bimaximal (BM), Tri-Bimaximal (TBM) and Golden Ratio (GR) form, and identify the leading corrections to such patterns that allow for a good fit to the leptonic mixing matrix as well as to the CP phase. We also show that the modified versions of BM, TBM and GR can easily accommodate the solar and atmospheric mass differences.

Abstract We present a simple extension of the Standard Model with three right-handed neutrinos in a SUSY framework, with an additional $$\hbox {U}(1)_\text {F}$$ U ( 1 ) F abelian flavor symmetry with a non standard leptonic charge $$L_e-L_\mu -L_\tau $$ L e - L μ - L τ for lepton doublets and arbitrary right-handed charges. Our model predicts an inverted neutrino mass hierarchy and it is able to reproduce the experimental values of the mixing angles of the PMNS matrix and of the $$r=\Delta m_\text {sun}^2/\Delta m_\text {atm}^2$$ r = Δ m sun 2 / Δ m atm 2 ratio, with only a moderate fine tuning of the Lagrangian free parameters. The baryon asymmetry of the Universe is generated via thermal leptogenesis through CP-violating decays of the heavy right-handed neutrinos. We present a detailed numerical solution of the relevant Boltzmann equation, accounting for the impact of the distribution of the asymmetry in the various lepton flavors.