244 research outputs found
Higgsless Models: Lessons from Deconstruction
This talk reviews recent progress in Higgsless models of electroweak symmetry
breaking, and summarizes relevant points of model-building and phenomenology.Comment: 12 pages, 2 figures, Presented at the X Mexican Workshop on Particles
and Field
Dynamical breakdown of Abelian gauge chiral symmetry by strong Yukawa interactions
We consider a model with anomaly-free Abelian gauge axial-vector symmetry,
which is intended to mimic the standard electroweak gauge chiral SU(2)_L x
U(1)_Y theory. Within this model we demonstrate: (1) Strong Yukawa interactions
between massless fermion fields and a massive scalar field carrying the axial
charge generate dynamically the fermion and boson proper self-energies, which
are ultraviolet-finite and chirally noninvariant. (2) Solutions of the
underlying Schwinger-Dyson equations found numerically exhibit a huge
amplification of the fermion mass ratios as a response to mild changes of the
ratios of the Yukawa couplings. (3) The `would-be' Nambu-Goldstone boson is a
composite of both the fermion and scalar fields, and it gives rise to the mass
of the axial-vector gauge boson. (4) Spontaneous breakdown of the gauge
symmetry further manifests by mass splitting of the complex scalar and by new
symmetry-breaking vertices, generated at one loop. In particular, we work out
in detail the cubic vertex of the Abelian gauge boson.Comment: 11 pages, REVTeX4, 10 eps figures; additional remarks and references
added; version published in Phys. Rev.
Does the three site Higgsless model survive the electroweak precision tests at loop?
We complete the list of one loop renormalization group equations and matching
conditions relevant for the computation of the electroweak precision parameters
and in the three site Higgsless model. We obtain one-loop formulas for
and expressed in terms of physical observables such as the KK gauge
boson mass , the KK fermion mass , and the KK gauge boson ()
couplings with light quarks and leptons . It is shown that these
physical observables, , and are severely constrained by
the electroweak precision data. Unlike the tree level analysis on the ideally
delocalized fermion, we find that perfect fermiophobity of is ruled out by
the precision data. We also study the cutoff dependence of our analysis.
Although the model is non-renormalizable, the dependence on the cutoff
parameter is shown to be non-significant.Comment: 13pages, 5figures, minor corrections made, references adde
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Three site Higgsless model at one loop
In this paper we compute the one loop chiral-logarithmic corrections to all O(p4) counterterms in the three site Higgsless model. The calculation is performed using the background field method for both the chiral and gauge fields, and using Landau gauge for the quantum fluctuations of the gauge fields. The results agree with our previous calculations of the chiral-logarithmic corrections to the S and T parameters in 't Hooft-Feynman gauge. The work reported here includes a complete evaluation of all one loop divergences in an SU(2)×U(1) nonlinear sigma model, corresponding to an electroweak effective Lagrangian in the absence of custodial symmetry. © 2007 The American Physical Society
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Flavor structure of the three-site Higgsless model
We study the flavor structure of the three-site Higgsless model and evaluate the constraints on the model arising from flavor physics. We find that current data constrain the model to exhibit only minimal flavor violation at tree level. Moreover, at the one-loop level, by studying the leading chiral-logarithmic corrections to chirality-preserving ΔF=1 and ΔF=2 processes from new physics in the model, we show that the combination of minimal flavor violation and ideal delocalization ensures that these flavor-changing effects are sufficiently small that the model remains phenomenologically viable. © 2012 American Physical Society
The Three Site Model at One-Loop
In this paper we compute the one-loop chiral logarithmic corrections to all
O(p^4) counterterms in the three site Higgsless model. The calculation is
performed using the background field method for both the chiral- and
gauge-fields, and using Landau gauge for the quantum fluctuations of the gauge
fields. The results agree with our previous calculations of the
chiral-logarithmic corrections to the S and T parameters in 't Hooft-Feynman
gauge. The work reported here includes a complete evaluation of all one-loop
divergences in an SU(2) x U(1) nonlinear sigma model, corresponding to an
electroweak effective Lagrangian in the absence of custodial symmetry.Comment: 40 pages, nine included eps figures. Minor corrections mad
One-Loop Corrections to the S and T Parameters in a Three Site Higgsless Model
In this paper we compute the the one-loop chiral logarithmic corrections to
the S and T parameters in a highly deconstructed Higgsless model with only
three sites. In addition to the electroweak gauge bosons, this model contains a
single extra triplet of vector states (which we denote \rho^{\pm} and \rho^0),
rather than an infinite tower of "KK" modes. We compute the corrections to S
and T in 'tHooft-Feynman gauge, including the ghost, unphysical
Goldstone-boson, and appropriate "pinch" contributions required to obtain
gauge-invariant results for the one-loop self-energy functions. We demonstrate
that the chiral-logarithmic corrections naturally separate into two parts, a
model-independent part arising from scaling below the \rho mass, which has the
same form as the large Higgs-mass dependence of the S or T parameter in the
standard model, and a second model-dependent contribution arising from scaling
between the \rho mass and the cutoff of the model. The form of the universal
part of the one-loop result allows us to correctly interpret the
phenomenologically derived limits on the S and T parameters (which depend on a
"reference" Higgs-boson mass) in this three-site Higgsless model. Higgsless
models may be viewed as dual to models of dynamical symmetry breaking akin to
"walking technicolor", and in these terms our calculation is the first to
compute the subleading 1/N corrections to the S and T parameters. We also
discuss the reduction of the model to the ``two-site'' model, which is the
usual electroweak chiral lagrangian, noting the ``non-decoupling''
contributions present in the limit as M_\rho goes to infinity.Comment: 58 pages; uses JHEP and axodraw. Extensively corrected to incorporate
consistent perturbative expansion, additional pinch contributions, and
running of delocalization parameter. Footnotes adde
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