Neutrino mass and invisible Higgs decays at the LHC

The discovery of the Higgs boson suggests that also neutrinos get their mass from spontaneous symmetry breaking. In the simplest ungauged lepton number scheme, the Standard Model (SM) Higgs has now two other partners: a massive CP-even, as well as the massless Nambu-Goldstone boson, called majoron. For weak-scale breaking of lepton number the invisible decays of the CP- even Higgs bosons to the majoron lead to potentially copious sources of events with large missing energy. Using LHC results we study how the constraints on invisible decays of the Higgs boson restrict the relevant parameters, substantially extending those previously derived from LEP and shedding light on spontaneous lepton number violation.