U(1) textures and lepton flavor violation - art. no. 116009.

U(1) family symmetries have led to successful predictions of the fermion ma ss spectrum and the mixing angles of the hadronic sector. In the context of the supersymmetric unified theories, they further imply a nontrivial mass structure for the scalar partners, giving rise to new sources of flavor vio lation. In the present work lepton flavor nontonserving_processes are exami ned in the context of the minimal supersymmetric standard model augmented b y a U(1)-family symmetry. We calculate the mixing effects on the mu-->e gam ma and tau-->mu gamma rare decays. All supersymmetric scalar masses involve d in the processes are determined at low energies using two loop renormaliz ation group analysis and threshold corrections. Further, various novel effe cts are considered and found to have important impact on the branching rati os. Thus, a rather interesting result is that when the seesaw mechanism is applied in the 12x12 sneutrino mass matrix, the mixing effects of the Dirac matrix in the effective light sneutrino sector are canceled at first order . In this class of models and for the case that soft term mixing is already present at the GUT scale, tau-->mu gamma decays are mostly expected to ari se at rates significantly smaller than the current experimental Limits. On the other hand, the mu-->e gamma rare decays impose important bounds on the model parameters, particularly on the supersymmetric scalar mass spectrum. In the absence of soft term mixing at high energies, the predicted branchi ng ratios for rare decays are, as expected, well below the experimental bou nds. [S0556-2821(99)08809-8].