The cascade seesaw mechanism generates neutrino mass for higher-dimension (5+4nn) operators through the tree-level diagram which brings the seesaw scale down to TeV. We investigate its collider signatures that are within reach of the LHC. In particular, both Type-II scalar and Type-III fermion seesaw signatures exist in such a scenario. Under the assumption that there are no mass splittings between the components in the scalar and fermion multiplets, we find that a multi-lepton final state from interplay of doubly charged scalar and heavy fermions can provide signatures distinguishable from conventional seesaw mechanisms.
Progress of Theoretical and Experimental Physics 103B02(2015)