Abstract
We reexamine the minimal Singlet + Triplet Scotogenic Model, where dark matter is the mediator of neutrino mass generation. We assume it to be a scalar WIMP, whose stability follows from the same {mathbb {Z}}_{2} symmetry that leads to the radiative origin of neutrino masses. The scheme is the minimal one that allows for solar and atmospheric mass scales to be generated. We perform a full numerical analysis of the signatures expected at dark matter as well as collider experiments. We identify parameter regions where dark matter predictions agree with theoretical and experimental constraints, such as neutrino oscillations, Higgs data, dark matter relic abundance and direct detection searches. We also present forecasts for near future direct and indirect detection experiments. These will further probe the parameter space. Finally, we explore collider signatures associated with the mono-jet channel at the LHC, highlighting the existence of a viable light dark matter mass range.
Highlights
“left-handed” neutrinos fails to pair-off.1 The presence of a massless neutrino has a very simple and clear implication concerning neutrinoless double beta (0ν2β) decay
In this work we have reexamined the generalized version of the minimal Singlet + Triplet Scotogenic Model, in which dark matter emerges naturally as the mediator of neutrino mass generation and its stability follows from the same Z2 symmetry responsible for the radiative origin of neutrino masses
While the simplest model of Ma [8] fails to be consistent over a wide range of parameters [10], our generalized scotogenic model is the minimal one allowing for a conserved Z2 symmetry all the way up to high mass scales [11]
Summary
If the lightest neutrino is massless, there is only one physical Majorana phase, and the effective mass parameter characterizing the amplitude for 0ν2β decay has a lower limit, even for a normal neutrino mass ordering, as currently preferred by oscillation data [3,4] This is in sharp contrast to the standard three-massive-neutrino-scenario in which there can be in general a destructive interference amongst the three light neutrinos (such cancellation in 0ν2β decay may be avoided in the three-massive-neutrino case in the presence of specific family symmetries [5,6,7]). We describe in detail the scalar and fermionic sector, as well as the radiative neutrino mass generation, emphasizing that the lightest neutrino is massless and discussing the resulting lower bound for neutrinoless double beta decay. The first Yukawa term Y αβ is the Standard Model interaction for leptons, which we can assume to be diagonal in flavor (Greek indices stand for family indices)
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