Connecting neutrino masses and dark matter by high-dimensional lepton number violation operator

We propose a new model with the Majorana neutrino masses generated at two-loop level, in which the lepton number violation (LNV) processes, such as neutrinoless double beta decays, are mainly induced by the dimension-7 LNV effective operator O-7 = (l) over bar (c)(R)gamma L-mu L(D-mu Phi)Phi Phi. Note that it is necessary to impose an Z(2) symmetry in order that O-7 dominates over the conventional dimension-5 Weinberg operator, which naturally results in a stable Z(2)-odd neutral particle to be the cold dark matter candidate. More interestingly, due to the non-trivial dependence of the charged lepton masses, the model predicts the neutrino mass matrix to be in the form of the normal hierarchy. We also focus on a specific parameter region of great phenomenological interests, such as electroweak precision tests, dark matter direct searches along with its relic abundance, and lepton flavor violation processes.