We suggest that dynamical breakdown of electroweak symmetry in an SU(3)xSU(2)xU(l) model of a single fermion family without fundamental scalars can reproduce the entire scalar sector of the standard model through fermion bound states and loop-induced couplings. The physical Higgs boson is essentially a it bound state. The top-quark and Higgs-boson masses are approximately 300 and 400 GeV, respectively. The strengths of the induced couplings among the scalars do not indicate a strongly interacting scalar sector.All experimental indications are that the standard model (SM) provides an adequate description of strong and electroweak interactions at all energy scales explored to date. Not every aspect of the SM has been tested, however. Perhaps the most crucial untested feature is the mechanism responsible for the spontaneous breakdown of electroweak symmetry. A key step toward verification of the SM would be the discovery of the physical Higgs boson (//), the one directly observable particle of the four fundamental scalars introduced into the theory to explain symmetry breaking.Should something resembling the H be discovered, however, it will have to be studied closely to determine whether it is indeed a fundamental particle. A composite H could well exist if the symmetry breaking is driven by a dynamical mechanism, rather than by fundamental scalars as in the SM. In models employing dynamical symmetry breaking (DSB), 1 the massless Goldstone states that become the longitudinal components of the W -and Z bosons are generally assumed to be fermionantifermion composites; conceivably the same dynamics that produces these composites could generate one or more composite //'s as well.In this Letter we discuss the properties of a composite Higgs boson that appears to exist in a particular electroweak model incorporating DSB. We argue that the couplings of the composite H to all other particles, when evaluated to a first approximation, are identical to the corresponding tree-level couplings of the fundamental H in the SM. Thus a composite H of this type would be very difficult to distinguish from a fundamental H.The model we consider 2 is based on the SU(3) xSU(2)xU(l) Lagrangian of the SM, minus all terms involving scalar fields. Note that omitting all reference to scalars means omitting all Yukawa couplings and scalar potential parameters. Thus, this model has fewer free parameters than the SM and, potentially, greater predictive power.We restrict our discussion to a one-family model in order to avoid complications that arise in the multifamily case, 2,3 but that are not relevant to the present discussion. As will become clear below, in order to make contact with experiment we should identify this single family with the third family (t,b,r, v r ).Unlike more conventional DSB models, particularly those based on the technicolor idea, 4 our model contains no QCD-like strong interaction at the TeV scale to which electroweak symmetry breaking is ascribed. We nevertheless assume that the symmetry-breaking selfenergies are of the...
This is the first in a series of papers dealing with four-dimensional quantum electrodynamics on a finite-element lattice. We begin by studying the canonical structure of the theory without interactions. This tells us how to construct momentum expansions for the field operators. Next we examine the interaction term in the Dirac equation. We construct the transfer matrix explicitly in the temporal gauge, and show that it is unitary. Therefore, fermion canonical anticommutation relations hold at each lattice site. Finally, we expand the interaction term to second order in the temporal-lattice spacing and deduce the magnetic moment of the electron in a background field, consistent with the continuum value of g = 2.
Int. J. Mod. Phys. A 1992.07:7561-7578. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ DAVIS on 02/03/15. For personal use only.
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