Quarks and leptons beyond the third generation

The possibility of additional quarks and leptons beyond the three generations already established is discussed. The make-up of this Report is (1) Introduction: the motivations for believing that the present litany of elementary fermions is not complete; (2) quantum numbers: possible assignments for additional fermions; (3) masses and mixing angles: mass limits from precision electroweak data, vacuum stability and perturbative gauge unification; empirical constraints on mixing angles; (4) lifetimes and decay modes: their dependence on the mass spectrum and mixing angles of the additional quarks and leptons; the possibility of exceptionally long lifetimes; (5) dynamical symmetry breaking: the significance of the top quark and other heavy fermions for alternatives to the elementary Higgs Boson; (6) CP violation: extensions to more generations and how strong CP may be solved by additional quarks; (7) experimental searches: present status and future prospects; (8) conclusions.     

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.     

Quarks

The Review summarizes much of particle physics and cosmology.Using data from previous editions,plus 3,062 new measurements from 721 papers,we list,evaluate,and average measured properties of gauge bosons and the recently discovered Higgs boson,leptons,quarks,mesons,and baryons.We summarize searches for hypothetical particles such as supersymmetric particles,heavy bosons,axions,dark photons,etc.All the particle properties and search limits are listed in Summary Tables.We also give numerous tables,figures,formulae,and reviews of topics such as Higgs Boson Physics,Supersymmetry,Grand Unified Theories,Neutrino Mixing,Dark Energy,Dark Matter,Cosmology,Particle Detectors,Colliders,Probability and Statistics.Among the 117 reviews are many that are new or heavily revised,including new reviews on Pentaquarks and Inflation.     

Quarks and reggeons

We propose a new algebra which will hopefully contribute to the joint understanding of electromagnetic and weak structure functions and of Regge couplings. It involves an infinite number of form factors of arbitrary complex spin J (with Re(J?1) > 0) and definite signature. The algebra holds exactly in a quark-gluon model when quantized canonically on equal light fronts. If all form factors have k = 0 and J = 1, the algebra closes and becomes U(6) × U(6), with the connecting subgroups being associated with pure quarks and pure antiquark currents, respectively. This doubling of the group leads to exact exchange degeneracy if baryons and mesons consist of qqq and q$\text{q}$ wave functions only.To some lowest approximation, Regge couplings can be calculated by representing U(6) × U(6) on properly mixed quark wave functions. With the mixing parameters fixed by the chiral subgroup, these couplings are determined up to an overall normalization.As an illustration, the coupling of the trajectories ?, ω; A₂, f; A₁, D; Z, Z_sg; π, η; B, H trajectories are estimated for the meson resonances ?, ω; π, η; A₂, f; A₁, D; B, H; A₀, σ. The trajectories π, η; B, H are not in the algebra initially but can be inferred from an extension of PCAC to the bilocal currents (“PCBC”).     

Strange Quarks and Lattice QCD

The last few years have seen a dramatic improvement in our knowledge of the strange form factors of the nucleon. With regard to the vector from factors the level of agreement between theory and experiment gives us considerable confidence in our ability to calculate with non-perturbative QCD. The calculation of the strange scalar form factor has moved significantly in the last 2 years, with the application of new techniques which yield values considerably smaller than believed for the past 20 years. These new values turn out to have important consequences for the detection of neutralinos, a favourite dark matter candidate. Finally, very recent lattice studies have resurrected interest in the famed H-dibaryon, with modern chiral extrapolation of lattice data suggesting that it may be only slightly unbound. We review some of the major sources of uncertainty in that chiral extrapolation.     

Quarks in stars

The basic parameters — mass and radius — of the quark configurations having central densities from 10¹⁹ to 10³² g/cm³ are obtained. It is shown that similar objects should have large gravitational mass defects. The curve of the stable configurations is extended to the region of densities substantially exceeding those of the nucleus.     

Quarks as quasiparticles

We attempt to jusify the quark model of hadrons, assuming that quarks are weakly interacting quasiparticles with no physical existence outside of hadrons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 94–99, August, 1988.     

Propagators and Masses of Light Quarks

Based on Dyson-Schwinger equations in “rainbow“ approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other.     

Propagators and Masses of Light Quarks

Based on Dyson-Schwinger equations in “rainbow” approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other.     

Quarks and gluons in color fields

Production and collective motion ofq \(\bar q\) and gluon pairs in strong color fields is studied using boost-invariant version of collisionless Boltzmann-Vlasov transport equations. It is shown that, for realistic fields, the effective formation time for pair production according to Schwinger mechanism is a small fraction of 1 fermi. Collective oscillations of quarkgluon gas, although damped by pair production and expansion of the system, remain an important feature of the process. The considered mechanism produces quark and gluons in a state which is rather far from equilibrium and thus strong collision effects (collision time ?1 fm) are needed to achieve equilibrated distributions at formation time. Finally, it is observed that, if such equilibrated distribution is produced at later times, the expansion of the system modifies dramatically its properties, as is explicitly shown for small oscillations of quark-gluon plasma in a weak external field.     

Leptonic CP-violation and mirror leptons

We study leptonic CP-violation within a single fermion generation in an extended electro-weak model where new right-handed leptons, so-called mirror leptons, exist and mix with standard left-handed leptons. Essential differences are pointed out between the mixing of a left-handed neutrino with a mirror neutrino in such a model and the ordinary mixing of two left-handed neutrinos in the standard model. E.g. in the mirror case CP-violation may occur even if neutrinos are Dirac particles. The number of physical CP-violation phases is determined for different mixing schemes and parameterizations of the leptonic weak currents in terms of these phases are presented.     

Magnetische Monopole und Quarks

We discuss the concept of Schwinger, which starts with the hypothesis of the existence of magnetical monopoles and results in a baryon model with magnetically charged constituents. Especially we analyse the mathematical consistency of such a theory. which admits a connection between some magnetically charged “quarks” and the homogeneous Maxwell-equations ?_v*F^μv(x^u) = 0, which, displaying a lack of symmetry with respect to the inhomogeneous one, ?_vF^μv(x^u) = 4?j^μ, are replaced by ?*j^μv. Here *j^μ(x^μ) means a conserved magnetic current which provides a monopole source for the magnetic field.     

夸克的半经典输运方程

对夸克的量子输运方程取半径典近似时保留到Wigner函数的一次微商项;在色空间和自旋空间展开这个半经典输运方程,得到了色单态自旋标量和色单态自旋矢量的输运方程:并把得到的结果和阿贝尔等离子体进行比较讨论了QGP的非阿见尔性质.