Quark and Lepton Masses from a {\boldmath $U(1)\times Z_2$} Flavor   Symmetry
  We show that solutions for the masses and mixings of the quarks and leptons based on a $U(1)\times Z_2$ horizontal symmetry are possible. The seesaw mechanism is shown to work consistently in the presence of the discrete symmetry. The discrete symmetry results in the phenomenologically useful suppressions of elements of the Yukawa matrices. The quark and lepton masses, the CKM mixing angles, and the neutrino mixing angles are accomodated at the order of magnitude level. 
Micheal S. Berger and Kim Siyeon