A New Two Higgs Doublet Model
  We propose an extension of the Standard Model by extending the EW symmetry to SU(2)_L x U(1) x Z_2 and introducing three SU(2)_L x U(1) singlet right handed neutrinos, N_R, and an additional Higgs doublet, phi. While the SM gauge bosons and the quarks and charged leptons acquire masses from the spontaneous breaking of SU(2)_L x U(1) symmetry at the electroweak scale, the neutrinos acquire masses from the spontaneous breaking of the discrete Z_2 symmetry at a scale of 10^{-2} eV. In addition to providing a new mechanism for generating tiny masses for the neutrinos, the model has interesting implications for neutrinoless double beta decay and the Higgs signals at high energy colliders, as well as in astrophysics and cosmology. 
S. Gabriel and S. Nandi