Testing New TeV-scale Seesaw Mediators at the LHC

We propose TeV-scale Dirac fermions producing Majorana masses of the known neutrinos via tree-level seesaw, different from standard type I and III seesaw. The employed weak five-plet with nonzero hypercharge leads to new seesaw formula m(nu) similar to v(6)/M-5 and to empirical masses m(nu) similar to 10(-1) eV for M similar to TeV new states. For a limited range of the parameter space, where M <= a few 100 GeV, the proposed mechanism is testable at the LHC via characteristic decays of Dirac type heavy leptons, produced by a Drell-Yan fusion.