We review two commonly used approximate treatments of beamstrahlung at lepton colliders. We discuss the applicability of those approximations and show that they are bound to fail at very high energy ee colliders such as CLIC. We model the beamstrahlung effects at CLIC by an exact numerical solution to the evolution equation for beamstrahlung and compare to the two approximations. We also discus...

We show that the Fritzsch texture of lepton mass matrices can naturally lead to the bi-large flavor mixing pattern, if three neutrinos have a normal but weak mass hierarchy (typically, m1 : m2 : m3 ∼ 1 : 3 : 10). The effective mass of the tritium beta decay and that of the neutrinoless double beta decay are too small to be observable in this ansatz, but CP violation at the percent level is allo...

We study the implications of having a similarity between quark and lepton mixing in the Dirac sector of the Standard Model plus the right-handed neutrino. This enable us to describe all masses and mixings in the Dirac sector in terms of only five parameters: three mass scales mb, mτ and mt, one parameter λ describing all the mixings, and a CP violating phase in the quark sector. Then, from expe...

We explore realizations of minimal flavour violation (MFV) for the lepton sector. We find that it can be realized within those seesaw models where a separation of the lepton number and lepton flavour violating scales can be achieved. We present a simple implementation of the MFV hypothesis that allows to reconstruct the flavour structure of the model from the values of the light neutrino masses...

The general analysis of lepton polarization asymmetries in rare B → K∗l+l− decay is investigated. Using the most general, model independent effective Hamiltonian, the general expressions of the longitudinal, normal and transversal polarization asymmetries for l and l+ and combinations of them are presented. The dependence of lepton polarizations and their combinations on new Wilson coefficients...

In supersymmetric theories with R-parity breaking, sleptons can be produced in quark-antiquark annihilation at the Tevatron through interactions in which two quark fields are coupled to a slepton field. If at the same time trilinear slepton-lepton-lepton couplings are present, the sleptons can be searched for as resonances in pp̄ → ν̃ → ll and τ̃ → lν final states. Existing Tevatron data can be ex...

We extend the effective theory of Minimal Lepton Flavor Violation (MLFV) by including four-lepton operators. We compute the rates for μ → 3e and τ → 3l decays and point out several new ways to test the hypothesis of MLFV. We also investigate to what extent it will be possible from (future) experimental information to pin down the contributions of different effective operators. In particular we ...

Abstract The tau lepton can be more composite than naively expected in models of strong electroweak symmetry breaking with tri-bimaximal lepton mixing. New leptonic resonances required by custodial symmetry, the tau custodians, can then be the first signal of this lepton flavor realization. Tau custodians can be very light, decaying almost exclusively into taus. The LHC reach for these new lept...

We study nuclear μ− − e− conversion in the general framework of an effective Lagrangian approach without referring to any specific realization of the physics beyond the standard model (SM) responsible for lepton flavor violation (Lf / ). We show that vector meson exchange between lepton and nucleon currents plays an important role in this process. A new issue of this mechanism is the presence o...

We study the Glashow-Iliopoulos-Maiani mechanism for flavor-changing neutral-current suppression in both the gauge and Higgs sectors, for models with SU(3)z, Igt U(1)iv gauge symmetry. The models di6'er from one another only with respect to the representation content. The main features of these models are that in order to cancel the triangle anomalies the number of families must be divisible by...