Bounds on the number and masses of quarks and leptons

We assume weak, electromagnetic and strong interactions to be asymptotically divergent, and to become strong at very large energies, of the order of the Plank mass. In this picture, the “low-energy” couplings (i.e. in the 10² GeV region) must be near the infrared stable point, and this allows us to put bounds on the number of elementary fermions (quarks and leptons). Similar assumptions on the Higgs couplings give bound on the fermion and on the Higgs boson masses. We consider the cases where weak and electromagnetic interactions are described by the gauge groups SU(2) ? U(1) or SU(2)_R ? U(1). The weak neutral current mixing angle is computed in both cases.     

The magnetic moment of composite leptons and quarks

We show that for a composite fermion of sufficiently small radius, the magnetic moment approaches the Dirac value corresponding to the overall charge and mass, regardless of the constituent values. This resolves a recently suggested difficulty in composite models of leptons and quarks.     

Pair production and vacuum polarization of vector particles with electric dipole moments and anomalous magnetic moments

The matrix 8-component Dirac-like form of the P-odd equations for boson fields of spin 1 and 0 are obtained and the symmetry group of the equations is derived. We found exact solutions of the field equation for vector particles with arbitrary electric and magnetic moments in external constant and uniform electromagnetic fields. The differential probability of pair production of vector particles with electric dipole moments and anomalous magnetic moments by an external constant and uniform electromagnetic field has been found using exact solutions. We have calculated the imaginary and real parts of the electromagnetic field Lagrangian that takes into account the vacuum polarization of vector particles. Received: 14 April 2001 / Revised version: 13 July 2001 / Published online: 19 September 2001     

Radiative corrections with two Higgs doublets at LEP/SLC and HERA

Formulae for the radiative corrections toe ⁺ e ^?→f \(\bar f\) andep→eX,v _e X′ are given for two Higgs doublets inSU(2)×U(1). The magnitude of deviations from the minimal model is discussed for theM _W ?M _Z mass correlation, thee ⁺ e ^? forward-backward and polarization asymmetries and σ(e ⁺ e ^? → hadrons) at LEP/SLC, and for σ(NC)/σ(CC), charge and polarization asymmetries in deep inelasticep scattering at HERA. Precision experiments can restrict the mass splitting between neutral and charged Higgs bosons to ?100 GeV. In the supersymmetric Higgs model the additional corrections remain unobservably small.     

Neutrino dipole moments and charge radii in non-commutative space-time

In this paper we obtain a bound TeV on the scale of space-time non-commutativity considering photon-neutrino interactions. We compute *-dipole moments and *-charge radii originating from space-time non-commutativity and compare them with the dipole moments calculated in the neutrino-mass extended standard model (SM). The computation depends on the nature of the neutrinos, Dirac versus Majorana, their mass and the energy scale. We focus on Majorana neutrinos. The *-charge radius is found to be at TeV.Received: 17 June 2004, Published online: 18 August 2004     

Heavy fermion contributions to the anomalous magnetic dipole and quadrupole moments of theW-boson

The contribution of a massivet-quark to the anomalous magnetic moment (Δκ) and the quadrupole moment (ΔQ) of theW-boson is calculated. An upper bound of Δκ=1.5×10^?2 and ΔQ=2.5×10^?3 for the standard model is obtained. Additional contributions from extraE ₆ fermions is also discussed.     

Topological characterization of leptons,quarks and hadrons

Electromagnetic-quantummechanical properties of the simplest topologically admissible field structures, based on quantized flux, relate Bohr- and muon-magneton to charges ±e (leptons), and ±e/3, ±2e/3, ±e/3 (quarks). Coaxial toroidal structures of pairs and triplets of quark fields characterize ordinary mesons and baryons. Also J/ψ, ? and jet structures fit into the concept of linkage of loops of quantized flux.     

Fourth generation of quarks and leptons

Permutation Symmetry sugests an intergeneration quark-lepton mass formulam _μ /m _τ /m _L =m _s /m _b /m _b′ =m _c /m _t /m _t′ . We consider several possibilities We consider several possibilities for the fourth generation masses.     

Constraints on composite models of quarks and leptons

The previously noted difficulty of obtaining Dirac magnetic moments in composite models is combined with the observation that a “light” bound fermion state with a small size must have the Dirac moment in a renormalizable theory since its anomalous moment is determined by its excitation spectrum. New constraints on composite models are given, including the decoupling of low-lying excitations and the “superconfinement” condition that creation of virtual electron-positron pairs by the superstrong gluons responsible for binding the constituents of the electron must be strictly forbidden in photon-electron scattering.     

Signals of excited quarks and leptons

e⁺e^? annihilation to two photons (including beam polarization) and quark-antiquark annihilation to gluons are discussed as possible tools to investigate the existence (and handedness) of excited electrons and quarks. Properties of these particles can also be explored in eγ and ep colliders; production cross sections and the impact of these particles on structure functions are derived.     

Current quark-mass dependence of nucleon magnetic moments and radii

A calculation of the current quark-mass dependence of nucleon static electromagnetic properties is necessary in order to use observational data as a means to place constraints on the variation of Nature’s fundamental parameters. A Poincaré-covariant Faddeev equation, which describes baryons as composites of confined quarks and nonpointlike diquarks, is used to calculate this dependence. The results indicate that, like observables dependent on the nucleons’ magnetic moments, quantities sensitive to their magnetic and charge radii, such as the energy levels and transition frequencies in hydrogen and deuterium, might also provide a tool with which to place limits on the allowed variation in Nature’s constants.     

Generations of massless composite quarks and leptons

We present a QCD-like composite model in which quarks, leptons and technifermions are three-body systems made out of three kinds of massless elementary fermions t, c and w, each carrying technicolor, color and weak gauge interactions, respectively. Discrete symmetries, remnants of the U(1)_A of the original lagrangian, are responsible for the masslessness of all the quarks and leptons and give the precise meaning of the generations. The model exhibits three generations for both quarks and leptons. Small but non-zero masses of the quarks and leptons are produced by the technicolor condensate of the composite technifermions, which thereby leads to the non-trivial Cabibbo mixing. Proton decays are all forbidden at the mass scale of the QCD-like theory.     

Four families of composite quarks and leptons

Four families of composite quarks and leptons, two standard and two non-standard, are found in a unique solution SU(3)_HC × SU(6)_L × SU(6)_R of a restricted 't Hooft anomaly-matching program. Testable predictions emerge, such as prohibition of μ → eγ, zero charge asymmetry in e⁺e^? → τ⁺τ^? in contrast to e⁺e^? → μ⁺μ^?, and a rich new hadron spectrum masses around M_W. A minimal set of spectator fermions contains color-singlet objects with fractional quark-like charges.     

A composite model of leptons and quarks

A heuristic model is presented, treating leptons and quarks as composites of spin $\text{1}\text{2}$ fields with charges 0, $\text{±}\text{e}\text{3}$. A distinguishability assumption leads to the emergence of three quark colors. The model is extended to consideration of the force-mediating bosons.