Abstract
Contrary to the see-saw models, extended Higgs sectors leading to radiatively-induced neutrino masses do require the extra particles to be at the TeV scale. However, these new states have often exotic decays, to which experimental LHC searches performed so far, focused on scalars decaying into pairs of same-sign leptons, are not sensitive. In this paper we show that their experimental signatures can start to be tested with current LHC data if dedicated multi-region analyses correlating different observables are used. We also provide high-accuracy estimations of the complicated Standard Model backgrounds involved. For the case of the Zee–Babu model, we show that regions not yet constrained by neutrino data and low-energy experiments can be already probed, while most of the parameter space could be excluded at the 95% C.L. in a high-luminosity phase of the LHC.
Highlights
Contrary to the see-saw models, extended Higgs sectors leading to radiatively-induced neutrino masses do require the extra particles to be at the TeV scale
This problem can be alleviated in models in which neutrino masses are suppressed by loop factors
If we enlarge the SM with only scalars, other than triplets with Y = 1, neutrino masses cannot arise at tree level
Summary
(Note that Dirac masses can not be induced by purely scalar extensions of the SM.) In particular, the following k decay modes take place in a variety of models: k±± → W±W±. It appears even in the simplest model, the see-saw type II, which extends the Higgs sec-. (Note that this value does not spoil the ρ parameter bound on this VEV, few GeV.) This decay mode appears naturally in extended composite Higgs models [37], which are further motivated by the gauge-hierarchy problem. As we will comment below, these are very hard to constrain experimentally
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