  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.
