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.     

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.     

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.     

Light composite fermions

In this paper we consider the possibility that QCD-like theories can lead to massless or near-massless composite fermions. The method of analysis relies on a conjectured equivalence between the confined and Higgs phases of certain non-abelian gauge theories. This “complementarity” principle allows us to analyze a theory as if the Higgs phenomenon occurred and then reinterpret the results in the language of composite gauge singlets. Those fermions which remain massless in the Higgs picture may then be interpreted as massless fermionic composites.The principle of complementarity, when applied to a class of extended technicolor models, implies that quarks and leptons are composites bound at a scale of order 1–100 TeV.     

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.     

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.     

A STRUCTURE MODEL OF STRATONS AND LEPTONS

A subquark model is proposed. According to this model, stratons and leptons are consisted of rishons T and V, which are multiplets of group SU_H(3)×SU_C(3)×SU_G(2)×SU(2)×U(1). Three generations of both stratons and leptons are obtained naturally. In this model, proton decay modes are μ^－e⁺e⁺ or e^－μ⁺μ⁺.     

ANOMALOUS WEAK CHARGED CURRENTS OF LEPTONS AND QUARKS IN A SUBSTRUCTURE MODEL

We present a general approach to get the anomalous weak charged current of leptons and quarks in a substructure mode1,in which quarks, leptons and W-bosons are composed of preons (fermions and scalar bosons). We have shown that the (V+A) current can be determined by the structure of leptons and quarks and the anomalous weak current can be very small. In particular, it can approach zero, if the wave function of leptons (or quarks) has aspinor structure (I-P/m_f)F.     

Composite fermions in Suzuki's preon model

We consider fermions in the preon model invented by Suzuki to describe electroweak vector bosons as composite objects. It turns out that composite fermions are in this model very heavy and cannot be interpreted as the ordinary quarks and leptons. This is the case both in Suzuki's original theory and in a modified theory introduced in this paper.     

Quarks and leptons as composite goldstone fermions

A dynamical scheme for composite quarks and leptons is proposed in which the observed fermions are Goldstone particles of spontaneously broken supersymmetry. Their residual interactions are described by a minimal effective lagrangian which invokes a non-linear realization of sypersymmetry. Possible experimental consequences are studied and it is found that the most conspicuous signature of this scheme would be a dramatic increase in the lepton pair production in hadronic collisions, particularly in $\text{pp}$ scattering, at high energy.     

Approximate global symmetries of the electroweak interactions

We discuss and exemplify a simple explanation for the approximate symmetries of the electroweak interactions that arises naturally in models in which the quarks, leptons and Higgs particles are all composite states of strongly interacting fermions.     

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.     

AN ANALYSIS OF FOUR-ELEMENT MODELS OF LEPTONS AND NON-DIAGONAL NEUTRAL CURRENTS

Due to the possible production of neutral and charge heavy leptons by v_μ, models consisting of four elements per "line", e.g. v_e, e^-, E⁰, E^- v_μ, μ^-, M^0, M^- v_τ, τ^-, T⁰, T^- ……are analysed. Non-diagonal neutral currents cannot be avoided. Nevertheless, a model is proposed within SU_（2）×U_（1） in which the process μ→eγ can still be suppressed by the Bjorken-Lane-Weinberg mechanism; various production cross-sections for heavy leptons are reasonable when compared with experiments. Models corresponding to SU_（3）×U（1） and still higher symmetries are discussed.     

SU(3) LEPTON MODEL AND THE DYNAMICAL GENERATION OF LEPTON MASS DIFFERENCES

A SU (3) lepton model is discussed in which the left- and right-handed leptons are on equal footing and sin²θ_w=1/4 is obtained. Dynamical symmetry breaking is investigated to see if lepton mass difference can be generated in this way so as to reduce the number of Higgs scalars and Yukawa coupling constants. Calculating the effective potential up to two-loop graphs gives the results that composite Goldstone bosons can exist only when the remained Yukawa coupling constant lies within a certain range. The corresponding heavy lepton mass obtained is about 130 GeV.     

A<Subscript>4</Subscript> model for the quark mass matrices

We propose a model for the quark masses and mixings based on an A₄ family symmetry. Three scalar SU(2) doublets form a triplet of A₄. The three left-handed-quark SU(2) doublets are also united in a triplet of A₄. The right-handed quarks are singlets of A₄. The A₄-symmetric scalar potential leads to a vacuum in which two of the three scalar SU(2) doublets have expectation values with equal moduli. Our model makes an excellent fit of the observed |V_ub/V_cb|. CP symmetry is respected in the charged gauge interactions of the quarks.     

A φ4-TYPE BAG MODEL OF HADRONS——THE “RUBBER BAG” MODEL（Ⅰ）——THEORY

In this paper a new bag model of hadrons,the“Rubber Bag”model,is proposed.This model treats each hadron as a bag system in the centre-of-mass frame.The bag,with its outer radius R_e and inner radius（R_c-D）,is characterized by its“averagesurface tension”T and the quarks are confined in it“temporarily”.This model isa field theoretical model which can also be used for quantitative calculations.Thus,ithas the merits of the SLAC bag model as well as those of the MIT bag model.     

A technocolor model with softly broken flavor symmetry

I describe an explicit technicolor model in which the interactions that give rise to the quark and lepton masses are generated by the exchange of massive gauge bosons as in extended technocolor models but in which the gauge bosons couple the quarks and leptons not directly to the technifermions, but to heavy fermions. Quark and lepton masses arise from box diagrams. The masses of the heavy fermions in this model come both from bare fermion mass terms and from the renormalizable interactions of a set of spinless fields. The model has a softly broken flavor symmetry that realizes the GIM suppression of FCNC effects as in a CTSM model.     

Quasi nambu-goldstone fermions

We explore in detail the hypothesis that quarks and leptons are the approximately massless quasi Goldstone fermions of a supersymmetric preon theory. In particular, we discuss the possible patterns of states emerging from the spontaneous breakdown of global symmetries in supersymmetric theories and construct the low-energy effective lagrangians describing the interaction of these states. In contrast to what happens in the Goldstone sector, the interactions of the quasi Goldstone fermions contain arbitrary parameters which directly reflect the preon dynamics. Various models are explored, including both models in which the weak interactions are residual and models where these interactions are fundamental. A variety of issues are addressed, from the universality and approximate SU(2)_L nature of the weak interactions, for the former class of models, to the generation of states beyond the quarks and leptons and the nature of the dynamical breaking of SU(2)_L×U(1), for the latter class of models. Open questions and speculations connected with the origin of families and the nature of fermion mass generation, including supersymmetry breaking, are also discussed.     

Asymptotic behavior of amplitudes for longitudinal-leptoquark processes and structure of the scalar sector in the minimal model involving four-color symmetry

Within the minimal model based on the four-color symmetry of quarks and leptons of the Pati-Salam type, the asymptotic behavior of amplitudes for processes involving longitudinal leptoquarks (and W or Z′ bosons) is investigated, together with the mechanism according to which the growth of these amplitudes at high energies is suppressed by scalar fields. It is shown that, within the Higgs mechanism of mass generation and of the mass splitting of quarks and leptons, the four-color symmetry of quarks and leptons requires that scalar-leptoquark doublets, scalar-gluon doublets, and an extra color-singlet scalar doublet exist in addition to the standard Higgs doublet.     

AN SU(4)×SU(2)×U(1) UNIFIED MODEL

In this paper we propose an SU(4)×SU(2)×U(1) unified model, in which the stratons and leptons of every generation belong to the same Multiplet, and the leptons will couple to the stratons. But this kind of coupling cannot cause the proton decay, and has only some effects in high energy scatterings. This model predicts the existense of two neutral intermediate bosons, instead of one, and the value of Weinberg angle to be sin²θ_w=0.25. The neutrinos have reasonable masses in the model.