Absolute neutrino mass scale and dark matter stability from flavour symmetry

We explore a simple but extremely predictive extension of the scotogenicmodel. We promote the scotogenic symmetry $\mathbb{Z}_2$ to the flavournon-Abelian symmetry $\Sigma(81)$, which can also automatically protect darkmatter stability. In addition, $\Sigma(81)$ leads to striking predictions inthe lepton sector: only Inverted Ordering is realised, the absolute neutrinomass scale is predicted to be $m_\text{lightest} \approx 7.5 \times 10^{-4}$ eVand the Majorana phases are correlated in such a way that $|m_{ee}| \approx0.018$ eV. The model also leads to a strong correlation between the solarmixing angle $\theta_{12}$ and $\delta_{CP}$, which may be falsified by thenext generation of neutrino oscillation experiments. The setup is minimal inthe sense that no additional symmetries or flavons are required.<br

Leptogenesis and muon (g−2)\boldsymbol{(g-2)} in a scotogenic model

We present a detailed study of a scotogenic model accommodating dark matter, neutrino masses and the anomalous magnetic moment of the muon while being consistent with the existing constraints on flavour violating decays of the leptons. Moreover, this model offers the possibility to explain the baryon asymmetry of the Universe via leptogenesis. We determine the viable regions of the model's parameter space in view of dark matter and flavour constraints using a Markov Chain Monte Carlo setup combined with a particular procedure to accommodate neutrino masses and the anomalous magnetic moment of the muon at the same time. We also discuss briefly the resulting collider phenomenology.Comment: 38 pages, 14 figure

Neutrino masses, flavor anomalies, and muon g-2 from dark loops

The lepton sector of the Standard Model is at present haunted by several intriguing anomalies, including an emerging pattern of deviations in b→sℓ ℓ processes, with hints of lepton flavor universality violation, and a discrepancy in the muon anomalous magnetic moment. More importantly, it cannot explain neutrino oscillation data, which necessarily imply the existence of nonzero neutrino masses and lepton mixings. We propose a model that accommodates all the aforementioned anomalies, induces neutrino masses and provides a testable dark matter candidate. This is achieved by introducing a dark sector contributing to the observables of interest at the 1-loop level. Our setup provides a very economical explanation to all these open questions in particle physics and is compatible with the current experimental constraints.Work supported by the Spanish Grants No. PID2020– 113775GB-I00 (AEI) and No. CIPROM/2021/054 (Generalitat Valenciana). A. V. acknowledges financial support from MINECO through the Ramón y Cajal contract No. RYC2018-025795-I. R. C. is supported by the Alexander von Humboldt Foundation Fellowship. The work of P. E. is supported by the Formación de Personal Investigador (FPI) Grant No. PRE2018-084599

Absolute neutrino mass scale and dark matter stability from flavour symmetry

We explore a simple but extremely predictive extension of the scotogenic model. We promote the scotogenic symmetry ℤ to the flavour non-Abelian symmetry Σ(81), which can also automatically protect dark matter stability. In addition, Σ(81) leads to striking predictions in the lepton sector: only Inverted Ordering is realised, the absolute neutrino mass scale is predicted to be m≈ 7.5×10 eV and the Majorana phases are correlated in such a way that |m| ≈ 0.018 eV. The model also leads to a strong correlation between the solar mixing angle θ and δ, which may be falsified by the next generation of neutrino oscillation experiments. The setup is minimal in the sense that no additional symmetries or flavons are required

Temperature effects on the Z2 symmetry breaking in the scotogenic model

It is well known that the scotogenic model for neutrino mass generation can explain correctly the relic abundance of cold dark matter. There have been claims in the literature that an important part of the parameter space of the simplest scotogentic model can be constrained by the requirement that no Z2-breaking must occur in the early universe. Here we show that this requirement does not give any constraints on the underlying parameter space at least in those parts, where we can trust perturbation theory. To demonstrate this, we have taken into account the proper decoupling of heavy degrees of freedom in both the thermal potential and in the RGE evolution

Systematic classification of two-loop d = 4 Dirac neutrino mass models and the Diracness-dark matter stability connection

We provide a complete systematic classification of all two-loop realizations of the dimension four operator for Dirac neutrino masses. Our classification is multi-layered, starting first with a classification in terms of all possible distinct two loop topologies. Then we discuss the possible diagrams for each topology. Model-diagrams originating from each diagram are then considered. The criterion for genuineness is also defined and discussed at length. Finally, as examples, we construct two explicit models which also serve to highlight the intimate connection between the Dirac nature of neutrinos and the stability of dark matter

Minimal 3-loop neutrino mass models and charged lepton flavor violation

We study charged lepton flavor violation for the three most popular 3-loop Majorana neutrino mass models. We call these models “minimal” since their particle content correspond to the minimal sets for which genuine 3-loop models can be constructed. In all the three minimal models the neutrino mass matrix is proportional to some powers of Standard Model lepton masses, providing additional suppression factors on top of the expected loop suppression. To correctly explain neutrino masses, therefore large Yukawa couplings are needed in these models. We calculate charged lepton flavor violating observables and find that the three minimal models survive the current constraints only in very narrow regions of their parameter spaces