Neutrino Mixing and Leptogenesis in $\mu-\tau$ Symmetry
  We study the consequences of the $Z_2$-symmetry behind the $\mu$--$\tau$ universality in neutrino mass matrix. We then implement this symmetry in the type-I seesaw mechanism and show how it can accommodate all sorts of lepton mass hierarchies and generate enough lepton asymmetry to interpret the observed baryon asymmetry in the universe. We also show how a specific form of a high-scale perturbation is kept when translated via the seesaw into the low scale domain, where it can accommodate the neutrino mixing data. We finally present a realization of the high scale perturbed texture through addition of matter and extra exact symmetries. 
E. I. Lashin (Ain Shams U., Cairo & Zewail City Sci. Technol., Giza &   ICTP, Trieste), N. Chamoun (HIAST & Bonn U.), C. Ham...
hep-ph