Regular Article - Theoretical Physics
Learning about flavour structure from τ→e β γ and μ→eγ?
IPNL, CNRS/IN2P3, Université de Lyon, Université Lyon 1, 4 rue E. Fermi, 69622, Villeurbanne cedex, France
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Published online: 22 February 2012
Current and upcoming experiments should improve the sensitivity to e α →e β γ decays by an order of magnitude. This paper assumes that one of the τ→e β γ decays is observed, and explores the structure and consequences of the required new flavoured couplings. In simple models (a low-scale seesaw, leptoquarks) it is shown that the dipole vertex function is proportional to a product of flavoured matrices from the Lagrangian (a “Jarlskog-like” invariant), provided that the loop particles are weakly coupled to the Higgs. Secondly, if the dipole vertex function has a hierarchical structure, this might imply that only some of the τ→e β γ modes can be observed, due to the “approximate zero” implied by the bound on μ→eγ. The assumptions underlying this potential test of a hierarchical structure are discussed.
© Springer-Verlag / Società Italiana di Fisica, 2012