ν-two Higgs doublet model and its collider phenomenology

Smallness of neutrino masses can be explained by introducing a tiny vacuum expectation value of an extra-Higgs doublet which couples to right-handed neutrinos (N-R). This situation is naturally realized in nu-Two Higgs Doublet Model (nu THDM), where a TeV-scale seesaw mechanism can work well. We investigate observable phenomenology of nu THDM at LHC and ILC experiments. Charged Higgs boson (H-+/-) in nu THDM is almost originated from the extra-Higgs doublet and its coupling strength to neutrinos are not small. Then this model induces rich phenomenology at the LHC, for example, when m(H +/-) < M-N, observable charged tracks can be induced from long lived charged Higgs. On the other hand, when m(H +/-) > M-N, right-handed neutrinos can be long-lived, and secondary vertices may be tagged at the LHC. The nu THDM also predicts observable lepton number violating process at the ILC.