Lepton Flavour Violation in the Constrained MSSM with Natural Neutrino Mass Hierarchy

Abstract

We present predictions for $\mu \to e \gamma$ and $\tau \to \mu \gamma$ in the CMSSM in which there is a natural hierarchy of neutrino masses resulting from the sequential dominance of three right-handed neutrinos. We perform a global analysis of this model in the $(m_0,M_{1/2})$ plane, assuming radiative electroweak symmetry breaking, and including all observed laboratory data. We confirm that a large (small) $\tau \to \mu \gamma$ rate results from the dominant right-handed neutrino being the heaviest (lightest) one. We show that the $\mu \to e \gamma$ rate may determine the order of the sub-dominant neutrino Yukawa couplings in the flavour basis, but may also be sensitive to effects beyond the leading log and leading mass insertion approximations. We also show that the $\mu \to e \gamma$ rate is independent of $\theta_{13}$, but measurement of this angle may determine a ratio of sub-dominant Yukawa couplings.