Neutrino Mass Operators of Dimension up to Nine in Two-Higgs-doublet Model

We study higher-dimensional neutrino mass operators in a low energy theory that contains a second Higgs doublet, the two Higgs doublet model. The operators are relevant to underlying theories in which the lowest dimension-five mass operators would not be induced. We list the independent operators with dimension up to nine with the help of Young tableau. Also listed are the lowest dimension seven operators that involve gauge bosons and violate the lepton number by two units. We briefly mention some of possible phenomenological implications.