Lepton-flavour symmetry in the Standard Model is broken by small masses for charged leptons and neutrinos. Introducing neutrino masses via dimension-5 operators associated to lepton-number violation at a very high scale, the corresponding coupling matrix may still have entries of order 1, resembling the situation in the quark sector with large top Yukawa coupling. As we have shown recently, in ...

We summarize the activities of the New Particles Subgroup at the 1996 Snowmass Workshop. We present the expectations for discovery or exclusion of leptoquarks at hadron and lepton colliders in the pair production and single production modes. The indirect detection of a scalar lepton quark at polarized e + e − and µ + µ − colliders is discussed. The discovery prospects for particles with two uni...

We construct a Z8 model for leptons where all Yukawa couplings are of order unity, but known lepton masses are generated radiatively, order by order. The seed is provided by fourth generation leptons E and N , which receive (Dirac) mass in usual way. Two additional Higgs doublets with nontrivial Z8 charge are introduced to give nearest neighbor Yukawa couplings. Hence, nonstandard Higgs bosons ...

The most promising scenarios of baryogenesis seems to be the one through lepton number violation. Lepton number violation through a Majarana mass of the right-handed neutrinos can generate a lepton asymmetry of the universe when the righthanded neutrinos decay. The left-handed neutrinos get small Majorana masses through see-saw mechanism in these models. A triplet higgs scalar violating lepton ...

We present a unified parametrization of quark and lepton mixing matrices. By using some simple relations between the mixing angles of quarks and leptons, i.e., the quark-lepton complementarity, we parametrize the lepton mixing matrix with the Wolfenstein parameters λ and A of the quark mixing matrix. It is shown that the Wolfenstein parameter λ can measure both the deviation of the quark mixing...

A natural explanation for the smallness of the neutrino mass requires them to be Majorana particles violating lepton number by two units. Since lepton number violation can have several interesting consequences in particle physics and cosmology, it is of utmost importance to find out if there is lepton number violation in nature and what is its magnitude. The neutrinoless double beta decay exper...

High precision electroweak tests, such as deviations from the Standard Model expectations of the Lepton Flavor Universality breaking in K → lνl (with l = e or μ), represent a powerful tool to test the Standard Model and, hence, to constrain or obtain indirect hints of New Physics beyond it. We explore such a possibility within Supersymmetric theories. Interestingly enough, a process that in its...

We re-analyze charged lepton corrections to neutrino mixing angles and CP phases, carefully including CP phases from the charged lepton sector. We present simple analytical formulae for including the charged lepton corrections and derive compact new results for small neutrino and charged lepton mixings θ 13 and θ e 13. We find a generic relation θ12 + 1 √ 2 θ e 12 cos(δ−π) ≈ θ 12, which relates...

The dimension-six CP-conserving SU L (2) × U Y (1) invariant operators involving the tau lepton are studied. It leads to the new physics effects to the lepton flavor violation (LFV) and lepton flavor-changing neutral current (FCNC). With the available experimental data on the decays Z → τ + + τ − , Z → µ + + µ − and µ − → e − + γ, the constraints on parameters of the effective lagrangian can be...