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Flavor Violating Transitions of Charged Leptons from a Seesaw Mechanism of Dimension Seven
A mechanism has been suggested recently to generate the neutrino mass out of
a dimension-seven operator. This is expected to relieve the tension between the
occurrence of a tiny neutrino mass and the observability of other physics
effects beyond it. Such a mechanism would inevitably entail lepton flavor
violating effects. We study in this work the radiative and purely leptonic
transitions of the light charged leptons. In so doing we make a systematic
analysis of the flavor structure by providing a convenient parametrization of
the mass matrices in terms of independent physical parameters and diagonalizing
them explicitly. We illustrate our numerical results by sampling over two CP
phases and one Yukawa coupling which are the essential parameters in addition
to the heavy lepton mass. We find that with the stringent constraints coming
from the muon decays and the muon-electron conversion in nuclei taken into
account the decays of the tau lepton are severely suppressed in the majority of
parameter space. There exist, however, small regions in which some tau decays
can reach a level that is about 2 orders of magnitude below their current
bounds.Comment: v1: 25 pages, 8 figures; v2: proofread version for PRD. Included
muon-electron conversion in nuclei at the referee's suggestion and added
relevant refs accordingly; main conclusion not changed but bounds on tau
lepton decays becoming more stringent; linguistic and editing corrections
also mad
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