This chapter of the report of the "Flavor in the era of the LHC" Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CPviolating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

We study possibility of observing the process h 0 → τ ± µ ∓ at a linear collider. The branching ratio is constrained to be of the order of 10 −4 by the τ − → µ − η result. Supersymmetric standard models can reproduce such amount of the branching ratio by taking a specific parameter set. The Higgsstrahlung process e + e − → Zh 0 is preferable because of its simple kinematic structure, then, the signal process is e + e − → Zh 0 → Zτ ± µ ∓ . The most serious background comes from the process, e + e − → Zh 0 → Zτ ± τ ∓ → τ ± µ ∓ νν. We estimate the significance of the signal, taking into account the background reduction.

We consider the MSSM with see-saw mechanism of neutrino mass generation and soft SUSY breaking with flavour-universal boundary conditions at the GUT scale, in which the lepton flavour violating (LFV) decays µ → e + γ, τ → µ + γ, etc., are predicted with rates that can be within the reach of present and planned experiments. These predictions depend critically on the matrix of neutrino Yukawa couplings Y ν which can be expressed in terms of the light and heavy right-handed (RH) neutrino masses, neutrino mixing matrix U PMNS , and an orthogonal matrix R. We investigate the effects of Majorana CP-violation phases in U PMNS , and of the RG running of light neutrino masses and mixing angles from M Z to the RH Majorana neutrino mass scale M R , on the predictions for the rates of LFV decays µ → e+γ, τ → µ+γ and τ → e+γ. Results for neutrino mass spectrum with normal hierarchy, values of the lightest ν-mass in the range 0 ≤ m 1 ≤ 0.30 eV, and quasi-degenerate heavy RH Majorana neutrinos in the cases of R = 1 and complex matrix R are presented. We find that the effects of the Majorana CP-violation phases and of the RG evolution of neutrino mixing parameters can change by few orders of magnitude the predicted rates of the LFV decays µ → e+γ and τ → e + γ. The impact of these effects on the τ → µ + γ decay rate is typically smaller and only possible for m 1 > ∼ 0.10 eV. If the RG running effects are negligible, in a large region of soft SUSY breaking parameter space the ratio of the branching ratios of the µ → e + γ and τ → e + γ (τ → µ + γ) decays is entirely determined in the case of R ∼ = 1 by the values of the neutrino mixing parameters at M Z .

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