Enhancing lepton flavor violation with the Z-penguin
Wed, Mar. 06th 2013, 14:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
Sizable rates for charged lepton flavor violating processes are expected in many neutrino mass models. High scale models, such as the classical supersymmetric seesaw, typically predict that the 3-body decays $l_i to 3 l_j$ have rates roughly a factor $alpha$ smaller than those of the 2-body channel $l_i to l_j gamma$. We show that $Z^0$-penguin diagrams can give an enhancement for decays $l_i to 3 l_j$ in many extensions of the Minimal Supersymmetric Standard Model (MSSM), breaking the previous expectation. $mu-e$ conversion in nuclei gets also enhanced by the same type of diagrams, becoming a very constraining observable in many scenarios. We demonstrate this effect in two models, namely, the supersymmetric inverse seesaw and R-parity violating supersymmetry. Finally, two issues are briefly discussed: the presence of this effect in non-supersymmetric models and the non-decoupling behavior of the $Z^0$-penguins.
Contact : ccaprini