Weak interactions of quasi nambu-goldstone fermions

We investigate the hypothesis that the observed weak interactions are the residual interactions of quasi Goldstone fermions. Left-handed quarks and leptons arise from the spontaneous symmetry breaking U(6) → U(4) × SU(2) in a supersymmetric theory. The simplest preon model realizing this breakdown leads, in the complementary picture, to the supersymmetric extension of the standard model of electroweak interactions. Furthermore, 't Hooft's anomaly conditions are satisfied with respect to the unbroken subgroup of the U(6) flavour symmetry and R-invariance. The preon model predicts the existence of a ninth chiral supermultiplet, the novino.     

The structure of weak interactions for composite quarks and leptons

We consider a model of quarks and leptons as quasi-Goldstone fermions which is based on an underlying supersymmetric SU(2)_HC × SU(2)′_HC preon theory. The spontaneous breakdown of a global U(6) × U(6)′ × U(1) symmetry to U(4) × U(4)′ × SU(2)_diag creates both quarks and leptons and at the same time allows for the possibility of having either residual or fundamental weak interactions. Effective lagrangians in the confining phase of the theory are compared to those emerging from a complementary picture and the problems connected with the nature of the weak interactions are discussed in this context also.     

Unification of families based on a coset space E7/SU(5) × SU(3) × U(1)

We show that the usual three families of quarks and leptons are identifiable with quasi Nambu-Goldstone fermions in a supersymmetric non-linear realization of E₇ corresponding to the Kähler manifold E₇/SU(5) × SU(3) × U(1). So the triplication of families suggests the underlying preon theory realizing the global E₇ linearly. Possible connections with N = 8 supergravity are also discussed.     

Complementarity in preon models with E6 metacolor

Tumbling complementarity is studied in chiral preon models based on the metacolor group E₆. By considering the breaking of E₆ into each maximal little group in the Higgs phase, several models are found that are in accord with complementarity. Three families of massless fermions (on the metacolor scale) can be obtained, but so far we have been unable to identify an E₆ × SU(N) preon model supported by complementarity that correctly predicts the quantum numbers of ordinary quarks and leptons.     

Repetition of the quark-lepton states in a supersymmetric composite model with complementarity

In a supersymmetric composite model based on an SU(4)^loc_sc confining theory, complementarity is used to support the symmetry-breaking pattern and spectrum of massless particles in a confining phase. The model is found to accomodate two generations of quarks and leptons as quasi Nambu-Goldstone fermions and another two generations as chiral fermions. Masses of composite particles are examined and the quark-lepton generations are classified according the possible mass splittings. The suppression of dangerous flavor-changing interactions is considered also.     

A supersymmetric left-right confining model of the weak interactions

We extend the supersymmetric, confining theory of weak interactions to a left-right symmetric model. This model is based on the gauge group SU(M)_SC×SU(2)_R×SU(2)_L×SU(3)_c×U(1) and is more natural as far as supersymmetry breaking is concerned. Supersymmetry protects chiral symmetries from spontaneous breakdown and allows a solution to the strong CP problem. This model can accommodate at most three generations of quarks and leptons.     

On the excited quarks and leptons

Using a duality-like finite energy sum rule, we discuss the assumption of having excited fermions at the W scale in a supersymmetric(SUSY) and non-supersymmetric hypercolour theory where quarks and leptons are bound states of fermion and scalar preon constituents. We conclude that a SUSY-like composite model cannot have excited fermions having a mass smaller than 0.5 TeV. A non-SUSY composite model having composite fermions but elementary W bosons can produce an excited fermion mass of the order of M_W provided that the scalar vacuum condensate is of the order of the (TeV)² scale of compositeness.     

Supersymmetric preon models with three-fermion generations

A class of supersymmetric preon models is considered in which the hypercolour groupG _HC and the unbroken flavour groupG _f anomalies are zero without needing spectators. It is shown that forG _HC=SU(2) and SU(3) quarks and leptons as composites can be obtained satisfying ’t Hooft’s anomaly matching conditions. For the case ofG _HC=SU(3),G _f can accommodate a horizontal symmetry group to describe just three generations.     

THE COMPOSITE MODEL OF LEPTON AND QUARK WITH ONLY ONE CONSTITUENT SCALAR

We propose a composite model of leptons and quarks containing two constituent fermions of spin 1/2 and a constituent scalar. The constituent fermions are massless and color singlets. Leptons, quarks and weak vector bosons are composites confined by SU(3)_H local gauge interaction, where leptons are made of three constituent fermions and quarks are two-body composites of a scalar and a fermion. The number of the constituent particles is less in our model. There are less exotic leptons and quarks. Quark-lepton parallelism holds. Weak interactions appear only at the composite level as residual short-range interactions among hypercolor singlets. The violation of parity occurs by the mechanism of dynamical symmetry breaking.     

SO(10)×SU(4) CHIRAL PREON MODEL SATISFYING COMPLEMENTARITY PRINCIPLE

We extended the MAC principle to the case for semisimple metacolor gauge group and the constructed and SO(10)×SU(4) chrial preon model which satisfies the complementarity principle.This model had a unique solution and thus predicted 4 generations of quarks and leptons without exotics.The generation gauge group was intruduced and the breaking of mass degeneracy among different generations was investigated.     

Quarks and leptons

We review the physics of quarks and leptons within the framework of gauge theories for the weak and electromagnetic interactions. The Weinberg-Salam SU(2) × U(1) theory is used as a “reference point” but models based on larger gauge groups, especially SU(2)_L × SU(2)_R × U(1), are discussed. We distinguish among thre “generations” of fundamental fermions: The first generation (e^?, ν_e, u, d), the second generation (μ^?, ν_μ, c, s) and the third generation (τ^?, ν_τ, t, b). For each generation we discuss the classification of all fermions, the charged and neutral weak currents, possible right-handed currents, parity and CP-violation, fermion masses and Cabibbo-like angles and related problems. We review theoretical ideas as well as experimental evidence, emphasizing open theoretical problems and possible experimental tests. The possibility of unifying the weak, electromagnetic and strong interactions in a grand unification scheme is reviewed. The problems and their possible solutions are presented, generation by generation, but a brief subject-index (following the table of contents) enables the interested reader to follow any specific topic throughout the three generations.     

Consequences of flavor as a dynamical quantum number

Phenomenological consequences of composite leptons and quarks are studied in the class of models in which the fermions of the first generation (i.e. e, ν_e, u and d) are the ground states of (unspecified) composite systems and each new generation is a radial excitation level. We find that the standard QED results remain practically unaffected in such a scheme. The excited quarks/leptons having mass larger than 5 GeV could be produced in e⁺e^- experiments and would increase the value of R by several per cent as compared with the case of the pointlike quarks and leptons. An argument is given for the smallness of the anomalous magnetic moments of composite leptons.     

Instantons,fermion mass generation and supercomplementarity

We consider the possibility that hypercolor instantons can provide fermion masses in preon models of quark and leptons. After discussing the basic ideas of this mechanism in a non-supersymmetric preon model we consider a supersymmetric, QCD-like preon model. We work within the so-called complementarity picture and show the equivalence between the mass term of the elementary fermions, generated by a vacuum expectation value of a elementary scalar, and the mass term of the composite fermions, generated by the hypercolor instantons.     

Natural suppression of flavour-changing neutral currents in supersymmetric gauge theories

Induced flavour-changing neutral currents (FCNC) in supersymmetric unified theories are investigated both in models with the standard SU(2)_L × U(1) gauge symmetry and in models with an extra ?(1) gauge symmetry. Supersymmetric extension of the natural flavour conservation laws for neutral currents is obtained by adding a condition regarding the assumed type of supersymmetry breaking. This condition ensures no direct flavour-changing couplings of neutral gauge-Higgs fermions and at the same time is necessary and sufficient for the natural suppression of the induced FCNC. It is found that in the class of models satisfying the new condition the contribution of the scalar partners of quarks to the induced strangeness-changing neutral current is comparable to that of the quarks in $\text{K}{}_{\mathrm{L}}\text{→ π}\text{π}$, while it is negligibly small in K_L ? K_S mass difference.     

A dynamical theory for the rishon model

We propose a composite model for quarks and leptons based on an exact SU(3)_C × SU(3)_H gauge theory and two fundamental $\text{J=}\text{1}\text{2}$ fermions: a charged T-rishon and a neutral V-rishon. Quarks, leptons and W-bosons are SU(3)_H-singlet composites of rishons. A dynamically broken effective SU(3)_C × SU(2)_L × SU(2)_R × U(1)_B?L gauge theory emerges at the composite level. The theory is “natural”, anomaly free, has no fundamental scalar particles, and describes at least three generations of quarks and leptons.     

Supersymmetric extension of the SU(3)×SU(2)×U(1) model

We describe a class of supersymmetric SU(3)×SU(2)×U(1) models where all quarks and leptons, as well as their scalar partners, get masses through one-loop radiative corrections.     

Study for Unified Preen Models

Two grand unified preon models with light quarks and leptons are presented.All these models have natural family structure at the composite level.One of them can give very low metacolor scale,Λ_MC～10⁴GeV.It is argued that the best choice for metacolor group is SU(4) and for unification group is SU(9).     

Weak interactions as manifestations of the substructure of leptons and quarks

A new model for the substructure of leptons, quarks and weak bosons is investigated. The weak interactions are residual effects due to the substructure. No spontaneous symmetry breaking is needed to generate masses. The structure of the weak interactions at high energies is expected to deviate substantially from the one predicted by the standard SU(2) × U(1) theory.     

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.