Lepton flavor violation in the supersymmetric grand unified models with a lopsided mass matrix

The tiny neutrino masses measured in neutrino oscillation experiments can be naturally explained via a supersymmetric seesaw mechanism. If supersymmetry breaking is mediated by gravity, such seesaw models may predict observable lepton flavor violating effects. In this work, we investigate the lepton flavor violating process mu-->egamma in supersymmetric seesaw models with a "lopsided" charged lepton mass matrix. Constraints set by the muon anomalous magnetic moment are taken into account. We find that such models generally predict a branching ratio for mu-->egamma far above the current experimental limit. Thus this process strongly constrains models of this type. Such restrictions suggest a novel form for the charged lepton mass matrix, featuring a "lopsided" structure for elements between both the 2-3 and the 1-3 generations. This structure produces a very small 1-3 mixing and a large 1-2 mixing in the charged lepton sector, leading naturally to a small Br(mu-->egamma) and to the large mixing angle solution for the solar neutrino problem.