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 .

Abstract. We analyse the cosmic-ray signatures of decaying gravitino dark matter in a model-independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying gravitinos to the gamma-ray spectrum, in particular a line at an energy below 300 GeV. Future measurements of the gamma-ray flux will provide important constraints on possible signatures of decaying gravitino dark matter at the LHC.

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We discuss whether the bi-maximal mixing given at GUT is consistent with the solar mixing at the normal side at the low energy. We consider the radiative corrections due to the τ -Yukawa, the neutrino-Yukawa and the slepton threshold corrections and discuss in what situation the maximal solar angle rotates towards the normal side. In this scheme, the |V 13 | and the Dirac CP phase δ are induced radiatively and we estimate these values.

We consider a model based on the supersymmetric QCD theory with N c = 2 and N f = 3. The theory is strongly coupled at the infrared scale Λ H . Its low energy effective theory below Λ H is described by the supersymmetric standard model with the Higgs sector that contains four iso-spin doublets, two neutral iso-spin singlets and two charged iso-spin singlets. If Λ H is at the multi-TeV to 10 TeV, coupling constants for the F-terms of these composite fields are relatively large at the electroweak scale. Nevertheless, the SM-like Higgs boson is predicted to be as light as 125 GeV because these F-terms contribute to the mass of the SM-like Higgs boson not at the tree level but at the one-loop level. A large non-decoupling effect due to these F-terms appears in the one-loop correction to the triple Higgs boson coupling, which amounts to a few tens percent. Such a non-decoupling property in the Higgs potential realizes the strong first order phase transition, which is required for a successful scenario of electroweak baryogenesis.Recently, the ATLAS and CMS experiments at the LHC [1] have reported an excess in the gamma-gamma mode at about 125 GeV, which may be a signal of the Higgs boson. In the Standard Model (SM), a light Higgs boson is the evidence of the weakly coupled Higgs sector. In models for physics beyond the SM, however, the light Higgs boson does not always correspond to a weakly coupled theory. The scenario based on little Higgs models [2] is an example of a strongly coupled theory with a light Higgs boson, where the Higgs boson arises as a pseudo Nambu-Goldstone boson originating from the breaking of some strongly interacting global symmetry at the TeV scale, and the Higgs boson mass is kept to be light. Supersymmetry (SUSY) is one of the most attractive candidates for the physics beyond the SM. SUSY can solve the gauge hierarchy problem, as the quadratic divergence in the radiative correction to the Higgs boson mass is cancelled owing to the non-renormalization theorem.In addition, elementary scalar fields are automatically introduced in the SUSY theory. The Higgs sector of the minimal SUSY extension of the SM (MSSM) necessarily contains two Higgs doublets. In the MSSM, the coupling constants in the Higgs potential are determined by the electroweak gauge couplings, and the mass of the SM-like Higgs boson is less than the Z boson mass at the tree level. With significant radiative corrections due to the large top Yukawa coupling [3], the Higgs mass can be pushed up to around 125 GeV in the case of very large stop masses or very large left-right stop mixing.Even within the framework based on SUSY, models with strongly coupled light Higgs boson can be constructed. A possible way is to introduce additional R-parity-even chiral superfields which strongly couple to the Higgs sector but the F-terms of which do not contribute to the Higgs boson four-point coupling. In this case, the SM-like Higgs boson is kept to be light. The strong couplings have rich phenomenological implications. First, radiative corrections...