By extending the electroweak gauge group to SU(3)L×U(1)Y , the 331 model incorporates dilepton gauge bosons Y which do not respect individual lepton family number. We point out that, in addition to family diagonal couplings such as Y –e–e that change lepton family number by two units, dileptons may also have family non-diagonal couplings such as Y –μ–e. The latter coupling violates lepton famil...

Precise measurements of the τ lepton properties provide stringent tests of the Standard Model structure and accurate determinations of its parameters. We overview the present status of a few selected topics: lepton universality, QCD tests and the determination of αs, ms and |Vus| from hadronic τ decays, and lepton flavor violation phenomena. In the Standard Model all lepton doublets have identi...

We present an implementation of the Yennie-Frautschi-Suura (YFS) scheme for all-orders resummation logarithms from emission soft real and virtual photons in processes that are critical future lepton colliders. They include, particular, e^-e^+\to f\bar{f} e−<...

We investigate the angular distribution of the lepton pair in the process p¯ p → γ * + X → ℓ + ℓ − + X, where the virtual photon is produced at high transverse momentum. The angular distribution of the leptons is very sensitive to possible nonperturbative effects, such as a nontrivial vacuum structure of QCD, and offers a good chance to test such effects. We present complete O(α 2 s) calculatio...

The lepton polarization asymmetry in the B → ℓ + ℓ − decay, when one of the leptons is polarized, is investigated using the most general form of the effective Hamiltonian. The sensitivity of the asymmetry to the new Wilson coefficients is studied.Moreover, correlations between the lepton polarization asymmetry and the branching ratio is studied. It is observed that, there are not exist such reg...

The lepton helicity distributions in the polarized Drell-Yan process at RHIC energy are investigated. For the events with relatively low invariant mass of lepton pair in which the weak interaction is negligible, only the measurement of lepton helicity can prove the antisymmetric part of the hadronic tensor. Therefore it might be interesting to consider the helicity distributions of leptons to o...

How is CP violation of low energy related to CP violation required from baryon number asymmetry ? We give an example which shows a direct link between CP violation of neutrino oscillation and baryogenesis through leptogenesis. When the sphaleron process is active, the sum of baryon number and lepton number is not a conserved quantity; d(B+L) dt = Anomaly = 0. Therefore, the evolution equation o...

In the analogous case of quark mixing via the CKM matrix, the smallness of the off-diagonal terms (small mixing angles) permits a “dominant eigenstate” approximation. Previous editions of this Review had assumed that the dominant eigenstate paradigm applies to neutrinos as well. However, the present results of neutrino oscillation searches show that the mixing matrix contains two large mixing a...

We investigate the constraints on four-Fermi contact interactions from low-energy lepton-quark and lepton-lepton scattering experiments — polarization asymmetries in electron (muon)-nucleon scattering experiments, cesium and thallium atom parity violation measurements, neutrino-nuclei and neutrino-electron scattering experiments. These constraints are then combined by assuming the lepton and qu...