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1.
We perform a variational calculation of the masses of glueballs of various spins and parities in SU(2) gauge theory. The quantum vacuum we use is generated by the lattice Monte Carlo technique. Our first results, obtained on medium sized lattices give m(0+) = (3.6 ± 0.35) Λmom, m(0? = (6.0 ± 1.0)Λmom, m(2+) = (6.5+1.8?1.1)Λmom, various mass upper bounds and information on glueball wave functions.  相似文献   

2.
M.K Volkov 《Annals of Physics》1984,157(1):282-303
On the basis of a effective “superconductivity”-type four-quark interaction, phenomenological Lagrangians are obtained for interactions of scalar, pseudoscalar, vector, and axial vector meson nonets. The Lagrangians include mass terms breaking chiral and U(3) invariance and corresponding to the quark masses mumdms. It is shown that upon introducing boson fields the masses of current quarks in the initial Lagrangian are replaced by the masses of constituent quarks in the phenomenological boson Lagrangians. Estimates of these masses are presented. Electromagnetic interactions are considered, and the vector dominance model is derived. The widths of various meson decays are calculated.  相似文献   

3.
It is suggested that in the usual type of gauge theory all fermions, including neutrinos, have right-handed components. The smallness or vanishing of the observed neutrino masses is explained by the fact that the appropriate neutral Higgs boson does not develop a non-zero vacuum expectation value. In the case when the neutrino masses do not vanish they are finite, of order GFm3, where m is the mass of the charged lepton. Non-conservation of lepton flavor gives rise to an instability of all neutrinos except ve and to μ→e+γ decay, but at a very low level.  相似文献   

4.
Quantum corrections generate a quadratically divergent mass term for the Higgs boson in the standard model. Thus, if the Higgs boson has a mass of order 100 GeV, it implies the presence of a cut-off of the theory around TeV scale, and some particles associated with the new physics may appear around the cut-off scale Λ. However, if Λ is several TeV, it may be difficult to find such particles at the LHC. In this Letter, we consider a situation in which the new physics provides relatively light particles compared with the scale Λ. In such a situation, we show that diphoton event and four lepton event by the decay of the Higgs and/or a new particle have naturally large cross section, and LHC may test the new physics in a considerably broad parameter region even if Λ is several TeV.  相似文献   

5.
We have calculated the glueball masses of various spins and parities in SU(3) gauge theory. Our first results give mM(0++)=(3.6±0.2)Λmom, mE(0++)=(4.3±0.3)Λmom, m(0?+)=(7.2?0.9+1.6)Λmom, mM(2++)=(8.1±1.1)Λmom and mE(2++)=(8.3?1.0+1.6)Λmom as well as information on the glueball wave functions.  相似文献   

6.
We present the order αs corrections to the masses of the Z and W bosons in the standard model. For the low mass quarks u, d, c and s the corrections are small and positive. Due to the Coulomb singularity which appears in the vector boson self-energy graph with one gluon exchange, we find a negative contribution from the t, b doublets.  相似文献   

7.
《Physics letters. [Part B]》1999,441(2-3):182-190
The upper and the lower bounds of the lightest CP-even Higgs-boson mass (mh) are discussed in the two-Higgs-doublet model (2HDM) with a softly-broken discrete symmetry. They are obtained as a function of a cut-off scale Λ (≤1019 GeV) by imposing the conditions in which the running coupling constants neither blow up nor fall down below Λ. In comparison with the standard model (SM), although the upper bound does not change very much, the lower bound is considerably reduced. In the decoupling regime where only one Higgs boson (h) becomes much lighter than the others, the lower bound is given, for example, by about 100 GeV for Λ=1019 GeV and mt=175 GeV, which is smaller by about 40 GeV than the corresponding lower bound in the SM. In generic cases, mh is no longer bounded from below by these conditions. If we consider the b constraint, small values of mh are excluded in Model II of the 2HDM.  相似文献   

8.
In order to investigate the Higgs mechanism nonperturbatively, we compute the Gaussian effective potential of the U(1) Higgs model (“scalar electrodynamics”). We show that the same simple result is obtained in three different formalisms. A general covariant gauge is used, with Landau gauge proving to be optimal. The renormalization generalizes the “autonomous” renormalization for λ?4 theory and requires a particular relationship between the bare gauge coupling e B and the bare scalar self-coupling λ B. When both couplings are small, then λ is proportional to e4 and the scalar/vector mass-squared ratio is of order e2, as in the classic 1-loop analysis of Coleman and Weinberg. However, as λ increases, e reaches a maximum value and then decreases, and in this “nonperturbative” regime the Higgs scalar can be much heavier than the vector boson. We compare our results to the autonomously renormalized 1-loop effective potential, finding close agreement in the physical predictions. The main phenomenological implication is a Higgs mass of about 2 TeV.  相似文献   

9.
A recently proposed model for dynamical breaking of chiral symmetry in QCD is extended and developed for the calculation of pion and chiral symmetry breaking parameters. The pion is explicitly realized as a massless Goldstone boson and as a bound state of the constituent quarks. We compute, in the limit of exact chiral symmetry, MQ, the constituent quark mass ?π the pion decay coupling, uu〉, the constituent quark loop density, μπ2/mq, the ratio of the Goldstone boson mass squared to the bare quark mass, and 〈r2π, the pion electromagnetic charge radius squared.  相似文献   

10.
《Nuclear Physics B》1996,461(3):407-436
We generalize the analytical expressions for the two-loop leading-log neutral Higgs boson masses and mixing angles to the case of general left- and right-handed soft supersymmetry breaking stop and sbottom masses and left-right mixing mass parameters (mQ, mU, mD, At, Ab). This generalization is essential for the computation of Higgs masses and couplings in the presence of light stops. At high scales we use the minimal supersymmetric standard model effective potential, while at low scales we consider the two-Higgs doublet model (renormalization group improved) effective potential, with general matching conditions at the thresholds where the squarks decouple. We define physical (pole) masses for the top quark, by including QCD self-energies, and for the neutral Higgs bosons, by including the leading one-loop electroweak self-energies where the top/stop and bottom/sbottom sectors propagate. For mQ = mU = mD and moderate left-right mixing mass parameters, for which the mass expansion in terms of renormalizable Higgs quartic couplings is reliable, we find excellent agreement with previously obtained results.  相似文献   

11.
Due to the absence of dimensional cut-off parameters in the dimensional regularization scheme, vanishing of the renormalized mass of the scalar boson implies vanishing of its renormalized mass; thus the masses of both bosons and fermions in renormalizable field theories can be made finite by multiplicative mass renormalizations. The improved renormalization group equations in D dimensions are derived in such a way that both the large (or the small) momentum limits and the Wilson ? expansions can be uniformly treated for the fermion as well as the boson cases. We discuss the improved equations for φ63 theory, φ44 theory, quantumelectrodynamics, massive vector-gluon model, and non-Abelian guage theories incorporating fermions. For the latter three classes of theories, the gauge dependent problem of the coefficient functions in the improved renormalization group equations is discussed.  相似文献   

12.
Electroweak symmetry breaking is attributed to dynamical generation of quark masses. Quarksq (and leptonsl) are assumed to be produced by hypercolor confinement of preons at an intermediate scaleΛ hc. Hierarchies observed in theq mass spectra can be explained by a BCS mechanism if the color interaction is enough asymptotically free and if residual ones emerging by the confinement are medium strong. The former assumption claims thatN≦4, whereN is the family number ofq andl. Dynamical equations to determineq masses and mixings are given, but they require knowledge on the physics atΛ hc. A phenomenological approach is also made on the basis of anSU(7)×SU(7) chiral preon model withN=4. The mass ratiom t/mb is related to (m c/m s)ηB withη B?1.1 andm t'/mb' to (m u/m d)ηA withη A?1.4. In this scheme the fourth down quark is the heaviest (~ 110 GeV) and contributes dominantly toF 2, whereF is the Fermi scale.  相似文献   

13.
《Physics letters. [Part B]》1987,196(2):157-162
The proposal that the neutrino owes the smallness of its mass to the spontaneous breaking of R parity in superstring models with an additional gauge boson coupled to the right-handed neutrino is analysed. The right-handed neutrino can not in general decouple from the low-energy theory in models with supersymmetry at the TeV scale and which possess the light Higgs doublets necessary for generating fermion masses. Experimental limits on neutrino mass then imply an upper limit on the new gauge boson mass mZr ⪅ 220 GeV.  相似文献   

14.
600 events of the rare electromagnetic decay η → μ+μ?γ have been detected. The branching ratio has been measured as BR(ημ+μ?γ) = (3.1 ± 0.4) × 10?4. The electromagnetic form factor of the η meson, F(mμμ2;0) = (1 ? mμμ2/Λ2)?1, has been determined. Λ = (0.72 ± 0.09) GeV/c2 is in good agreement with the vector meson dominance model.  相似文献   

15.
We estimate hadronic self-energy effects to “bare” pseudoscalar (P) and vector (V) meson states due to theP→PV→P, P→VV→P, V→ PP→V, V→PV→V andV→VV→V loops. We simulate higher order diagrams by consistently requiring external and internal particles to have the same mass. We find good agreement with all the experimental masses (exceptm π), widths and mixing angles. The “bare”P andV states are heavy (≈1.26 GeV) and degenerate up to a smallm s?mu quark mass difference term. The “bare” coupling constants for thePPV, PVV andVVV vertices obey exact OZI rule and almost exact SU(6) W symmetry. We use a common cut-off ofk cm?0.7 GeV/c corresponding to a harmonic oscillator radius of ?0.7 fm for all SU(6) W related thresholds except for the pion.  相似文献   

16.
The existence of dark matter is explained by a new neutral vector boson, C-boson, of mass (900 GeV), predicted by the Wu mechanisms for mass generation of gauge field. According to the Standard Model (SM) W, Z-bosons normally get their masses through coupling with the SM Higgs particle of mass 125 GeV. We compute the self-annihilation cross section of the vector gauge boson C-dark matter and calculate its relic abundance. We also study the constraints suggested by dark-matter direct-search experiments. The problem on the stability of C-particle is left as an open question for future research.  相似文献   

17.
《Nuclear Physics B》1988,299(1):7-20
We analyze the high-energy behaviour of vector boson scattering amplitudes within the framework of a recently suggested lagrangian model based on global weak isospin symmetry broken by electromagnetism. Requiring vanishing of the most strongly (as s2) rising contribution to vector boson scattering amplitudes leads to vector boson self-interactions dependent on a single parameter, for which the anomalous W± magnetic moment, κ, can be chosen. Tree unitarity is violated at about 2 TeV for arbitrary κ as in the SU(2)L × U(1)Y theory for mH → ∞. The model is well suited for significant tests of the vector boson sector of the SU(2)L × U(1)Y electroweak theory in processes such as e+e → W+W.  相似文献   

18.
It is shown that a classical relativistic charged particle has an anomalous magnetic moment g=4α/3. If such a “dressed” particle with its mass m, charge e, and anomalous magnetic moment g is quantized by a generalized Dirac equation, then the wave equation predicts a second mass mμ=me(3/2α+1). It is suggested that a magnetic portion of the self-energy is quantized.  相似文献   

19.
We prove that the Schwinger functions for the ultraviolet cut-off exponential interaction with euclidean measure exp {;?λΛ:eαξk(x):dx} dμ0(ξ/ ∫ exp{?λΛ:eαξk(x):dx} dμ0(ξ), λ > 0, converge as the ultraviolet cut-off is removed. The limits are the free Schwinger functions in the case of space-time dimension n ? 3. In the case n = 2 this holds for |α| sufficiently big, whereas for |α| < 2 √π, one has the well-known nontrivial Schwinger functions of the exponential interaction.  相似文献   

20.
《Physics letters. [Part B]》1999,459(4):589-593
It is shown that the principal pattern in baryon spectroscopy, which is associated with the flavor-spin hyperfine interactions, is due to the spontaneous breaking of chiral symmetry in QCD and persists in the chiral limit. All corrections, which are associated with a finite quark (Goldstone boson) mass are suppressed by the factor (μ/Λχ)2 and higher.  相似文献   

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