Same-Sign Tetra-Leptons from Type II Seesaw

The type II seesaw mechanism introduces a hypercharged Higgs triplet to explain the observed neutrino masses and mixing. Among three triplet components, the doubly charged Higgs boson can be the lightest and decay mainly to same-sign di-leptons. Furthermore, the heavier singly charged or neutral Higgs boson produces a doubly charged Higgs boson through its fast gauge decay. This leads to a novel signature of same-sign tetra-leptons resulting from a pair production of same-sign doubly charged Higgs bosons caused by the nearly degenerate neutral scalar mixing which can be sizable for an appropriate choice of the model parameters. After studying production cross-sections for the same-sign tetra-lepton signal in the parameter space of the mass splitting among triplet components and the triplet vacuum expectation value, we provide a LHC analysis of the same-sign tetra-lepton signal for a benchmark point chosen to maximize the event number.