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1.
Assuming that leptons are composed of a heavy fermion and a heavy scalar boson and using Bethe-Salpeter equation, we conclude that in the non-relativistic limit the radius and , in particular, the anomalous magnetic moment of leptons can be sufficiently small provided that the interaction of the constituents is of vector type and that the fermion is much beavier than the scalar boson. Whereas the scalar type interaction can only give wavefunctions with large radius and anomalous magnetic moment.  相似文献   

2.
《Nuclear Physics B》1988,307(2):365-375
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.  相似文献   

3.
We present a SUSY model with four Higgs doublets of the"private type,"in which all fermion types(up,down,and charged leptons)obtain their masses from a different Higgs doublet H_f(f=u_1,d,e) .The conditions for anomaly cancellation imply that the remaining Higgs doublet of the model( Hu_2 )must have the same hypercharge as Hu_1 ,and thus,can only couple to up-type quarks,which opens the possibility to have FCNCs only in this sector.We study the Lagrangian of the model,and in particular,the Higgs potential,to identify the Higgs mass-eigenstates and their interactions;for the Yukawa matrices,we consider the four-texture case.We obtain constraints on the model parameters by using LHC measurements on the properties of the 125 GeV Higgs boson(h),and identify viable regions of the parameter space.Subsequently,these constraints are used to evaluate the prospects for detecting the FCNC decay mode t→ch at the future high-luminosity(HL)option for the LHC,which are compared with current limits from LHC-run2.Moreover,we evaluate the FCNC decay of the next heavier Higgs boson H2→tc ,which can typically reach BR(H_2→tc)≈(10-4-10-5) .The search for the signal at HL-LHC is also studied,and it is found that it may be detectable for specific regions of the model parameter space.  相似文献   

4.
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.  相似文献   

5.
We propose an ETC model based on SO(10)2 which naturally accomodates a complete family of technifermions in the 7 of SO(7)TC plus three generations of quarks and leptons. The technicolor sector corresponds to one of the examples recently shown by Appelquist et al. to avoid the flavor-changing neutral-current problem. In order to obtain an interesting fermion mass spectrum we propose a composite version of the ETC model based on SO(10)3.  相似文献   

6.
A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb at an centre-of-mass energy of 183 GeV and about 20 pb equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/ and 90 GeV/, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermion to its mass () as a function of the mass. Received: 30 October 1998 / Published online: 1 March 1999  相似文献   

7.
We suggest a mechanism whereby the three generations of quarks and leptons correspond to surface modes in a five-dimensional theory. These modes arise from a nonlinear fermion dispersion relation in the extra dimension, much in the same manner as fermion surface modes in a topological insulator or lattice implementation of domain wall fermions. We also show that the topological properties can persist in a deconstructed version of the model in four dimensions.  相似文献   

8.
The massive Gross-Neveu model is solved in the large-N limit at finite temperature and chemical potential. The scalar potential is given in terms of Jacobi elliptic functions. It contains three parameters which are determined by transcendental equations. Self-consistency of the scalar potential is proved. The phase diagram for non-zero bare quark mass is found to contain a kink-antikink crystal phase as well as a massive fermion gas phase featuring a cross-over from light to heavy effective fermion mass. For zero bare quark mass, we recover the three known phases kink-antikink crystal, massless fermion gas, and massive fermion gas. All phase transitions are shown to be of second order. Equations for the phase boundaries are given and solved numerically. Implications on condensed matter physics are indicated where our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.  相似文献   

9.
Wave equations make it possible to ascribe the quantum numbers to leptons theoretically. Minimal extension of the groups describing stable leptons led to three new types of groups. Each of them has an appropriate structure invariant ±1.0 and its own set of substructures having a physical interpretation in terms of stable leptons. The properties of the above-mentioned groups allow one to generate new types of equations and to relate them with two doublets (particle-antiparticle) of massive, charged unstable leptons and a doublet of massive unstable neutrinos.  相似文献   

10.
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.  相似文献   

11.
《Nuclear Physics B》1986,269(1):109-118
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.  相似文献   

12.
提出一种新的包含三代已知轻子与夸克的SU(5)大统—模型.按本模型,强子可看作由夸克形成的非拓扑孤粒子;轻子与夸克本质上是相同的,它们之间的差别是由对称性自发破缺造成的;在强子内部,夸克质量很小,其性质与已知夸克相同;在强子外部,夸克的性质与已知轻子相同,只是质量很重,并将很快衰变.本文除了定义严格守恒的电荷Q0、费米子数F0外,还在孤粒子内部定义了近似守恒的内色荷、内电荷、内费米子数.已知SU(5)大统—模型的(L-B)守恒相应于本模型的F0守恒。  相似文献   

13.
A new grand unified model containing the known three generations of quark and lepton in which hadrons are regarded as nontopological solitons formed from quarks is presented. According to the model leptons and quarks are the same in essence. The differences between them are caused by spontaneous symmetry breaking.When a quark is located inside a hadron, its properties will be the same as those of a known quark and its mass very small. When a quark is outside hadrons, its properties will be the same as those of a known lepton, its mass very large and it Will rapidly decay. Except defining charge Q0 and fermion number F0 which are exactly conserved, we also define interior colour, interior charge and interior fermion number approximatly conserved inside a hadron. The (L-B) conservation in the known SU(5) model corresponds to the fermion number number Fo conservation in the present model.  相似文献   

14.
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.  相似文献   

15.
In models of weak and electromagnetic interactions with six or more quarks, universality and, in some cases, the V-A structure of leptonic and semi-leptonic interactions have to be put in by hand. We show how both properties remerge naturally if replacing the usual SU(2) weak isospin group by a large SU(4) group, which also lends itself quite naturally to grand unifications (including strong interactions). The model needs eight quarks and two charged heavy leptons, and features, nesides universality and V-A, non-equality of neutral current scattering of ν's on leptons and on hadrons, and very reasonable relations for (bare) fermion masses.  相似文献   

16.
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 MW provided that the scalar vacuum condensate is of the order of the (TeV)2 scale of compositeness.  相似文献   

17.
We study the possibility of the existence of extra fermion families and an extra Higgs doublet. We find that requiring the extra Higgs doublet to be inert leaves space for three extra families, allowing for mirror fermion families and a dark matter candidate at the same time. The emerging scenario is very predictive: It consists of a standard model Higgs boson, with a mass above 400 GeV, heavy new quarks between 340 and 500 GeV, light extra neutral leptons, and an inert scalar with a mass below M(Z).  相似文献   

18.
Starting from a generalization of helicity to the case of spacelike momenta we give the spin density operator for the virtual photon in inelastic scattering of polarized, massive leptons.  相似文献   

19.
The massive Schwinger model is considered in the infinite momentum frame. By assuming its physical particles consist of two fermion bound states, we compute a spectrum. For fermions with large bare masses, the method is reliable. For low-mass fermions, we find we must include states of higher fermion number to adequately describe excited states of the fundamental boson of the theory. We do this for the scalar state in the limit of small bare fermion mass. This representation of the theory provides a unified treatment of both the weak and strong coupling limits, remaining in the fermion representation throughout. We have checked our numerical results with exact calculations wherever possible, and find good agreement.  相似文献   

20.
A complete set of fermion and Higgs superfields is introduced with well-defined SO(10) properties and U(1)xZ2xZ2 family charges from which the Higgs and Yukawa superpotentials are constructed. The structures derived for the four Dirac fermion and right-handed Majorana neutrino mass matrices coincide with those previously obtained from an effective operator approach. Ten mass matrix input parameters accurately yield the twenty masses and mixings of the quarks and leptons with the bimaximal atmospheric and solar neutrino vacuum solutions favored in this simplest version.  相似文献   

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