Tribimaximal neutrino mixing from a supersymmetric model with $A_4$ family symmetry

In the supersymmetric seesaw model of neutrino masses, augmented by the non-Abelian discrete tetrahedral symmetry $A_4$, a specific pattern of neutrino mixing is automatically generated if one of the three heavy singlet neutrino superfields acquires a nonzero vacuum expectation value. This pattern turns out to be exactly that of tribimaximal mixing, i.e. ${sin}^2{\theta }_{23}=1/2$, ${sin}^2{\theta }_{12}=1/3$, and ${sin}^2{\theta }_{13}=0$, in good agreement with data.