Q6 flavor symmetry model for the extension of the minimal standard model by three right-handed sterile neutrinos

The extension of the minimal standard model by three right-handed sterile neutrinos with masses smaller than the electroweak scale (nu MSM) is discussed in a Q(6) flavor symmetry framework. The lightness of the keV sterile neutrino and the near mass degeneracy of two heavier sterile neutrinos are naturally explained by exploiting group properties of Q(6). A normal hierarchical mass spectrum and an approximately mu-tau symmetric mass matrix are predicted for three active neutrinos. Nonzero theta(13) can be obtained together with a deviation of theta(23) from the maximality, where both mixing angles are consistent with the latest global data including T2K and MINOS results. Furthermore, the tiny active-sterile mixing is related to the mass ratio between the lightest active and lightest sterile neutrinos.