53 research outputs found
S and T Parameters from a Light Nonstandard Higgs versus Near Conformal Dynamics
We determine the contribution to the and parameters coming from
extensions of the standard model featuring a light nonstandard-like Higgs
particle. We neatly separate, using the Landau gauge, the contribution from the
purely nonstandard Higgs sector, from the one due to the interplay of this
sector with the standard model. If the nonstandard Higgs sector derives from a
new type of near conformal dynamics, the formalism allows to precisely link the
intrinsic underlying contribution with the experimentally relevant parameters.Comment: 13 pages, 3 figure
An Effective Higgsless Theory: Satisfying Electroweak Constraints and a Heavy Top Quark
The main challenge faced by Higgsless models of electroweak symmetry breaking
is to reconcile the experimental constraints imposed by the precision
electroweak data and the top quark phenomenology with the unitarity constraints
imposed by longitudinal gauge boson scattering amplitudes. In this paper we
expand on previous work, giving details of how delocalized fermions can be used
to adjust the parameter to zero, while keeping the and parameters
naturally suppressed. We also show that it is possible to obtain the top quark
mass, without affecting the delay of unitarity violation of the scattering amplitude, by separating the mass scales of the fermion
sector () from that of the gauge sector (). The fermion sector
scale is only weakly constrained by unitarity of the scattering amplitude; thus the ratio can be quite large, and the
top mass can be easily achieved. Anomalous right-handed couplings involving the
third generation quarks also avoid constraints from experimental data if
is sufficiently large.Comment: 26 pages, JHEP forma
Probing Near-Conformal Technicolor through Weak Boson Scattering
The recently observed boson at 125 GeV could be a light composite scalar from
near-conformal technicolor dynamics: a technicolor Higgs. If this is the case,
unitarization of longitudinal weak boson scattering amplitudes, which is due to
exchanges of the Higgs and spin-one vector technimesons, is expected to occur
in a strong regime, with saturation of the unitarity bounds. This implies that
processes, where is either a or a boson, are
enhanced, relative to the standard model. We show that this allows probing
near-conformal technicolor for couplings and masses of the spin-one resonances
which are not directly accessible for direct Drell-Yan production.Comment: 19 pages, 4 figure
WW Scattering in Walking Technicolor
We analyze the WW scattering in scenarios of dynamical electroweak symmetry
breaking of walking technicolor type. We show that in these theories there are
regions of the parameters space allowed by the electroweak precision data, in
which unitarity violation is delayed at tree level up to around 3-4 TeV without
the inclusion of any sub-TeV resonances.Comment: 2 Columns RevTeX, 10 pages, 9 Figure
Unitarity in Technicolor
We investigate the longitudinal scattering in models of dynamical
electroweak symmetry breaking featuring a spin one axial and vector state and a
composite Higgs. We also investigate the effects of a composite spin two state
which has the same properties of a massive graviton. Any model of dynamical
electroweak symmetry breaking will feature, depending on the dynamics, some or
all these basic resonances as part of the low energy spectrum. We suggest how
to take limits in the effective Lagrangian parameter space to reproduce the
dynamics of different types of underlying gauge theories, from the traditional
Technicolor models to the newest ones featuring nearly conformal dynamics. We
study the direct effects of a light composite Higgs and the indirect ones
stemming from the presence of a light axial resonance on the longitudinal
scattering.Comment: 23 pages, 5 figure
Technicolor Dark Matter
Dark Matter candidates are natural in Technicolor theories. We introduce a
general framework allowing to predict signals of Technicolor Dark Matter at
colliders and set constraints from earth based experiments such as CDMS and
XENON. We show that the associate production of the composite Higgs can lead to
relevant signals at the Large Hadron Collider.Comment: RevTeX, 4 pages, 6 figures. New figure one with added the projected
data for superCDM
Constraining Walking and Custodial Technicolor
We show how to constrain the physical spectrum of walking technicolor models
via precision measurements and modified Weinberg sum rules. We also study
models possessing a custodial symmetry for the S parameter at the effective
Lagrangian level - custodial technicolor - and argue that these models cannot
emerge from walking type dynamics. We suggest that it is possible to have a
very light spin-one axial vector boson. However, in the walking dynamics the
associated vector boson is heavy while it is degenerate with the axial in
custodial technicolor.Comment: Two columns, RevTex, 4 pages, 5 eps file
125 GeV Higgs from a not so light Technicolor Scalar
Assuming that the observed Higgs-like resonance at the Large Hadron Collider
is a technicolor isosinglet scalar (the technicolor Higgs), we argue that the
standard model top-induced radiative corrections reduce its dynamical mass
towards the desired experimental value. We then discuss conditions for the
spectrum of technicolor theories to feature a technicolor Higgs with the
phenomenologically required dynamical mass. We use scaling laws coming from
modifying the technicolor matter representation, number of technicolors,
techniflavors as well as the number of doublets gauged under the electroweak
theory. Finally we briefly summarize the potential effects of walking dynamics
on the technicolor Higgs.Comment: ReVTex, 15 pages, 3 figures. Version to match the published on
Constraints on Little Higgs with Fully-Radiative Electroweak Symmetry Breaking
In a recent paper, we introduced a new Little Higgs model, which contains the
gauge structure , embedded in an approximate global
symmetry. After breaking to the standard model, , this produces two heavy bosons and two heavy
bosons, along with a single Standard Model-like Higgs scalar.
The unique feature of the model was that it was possible to obtain electroweak
symmetry breaking and a light Higgs mass entirely from perturbative loop
contributions to the Higgs effective potential. In this paper we consider the
electroweak constraints on this model, including tree and loop contributions to
the universal oblique and non-oblique parameters, tree-level corrections to the
vertex, and tree and loop level corrections to . The most
significant corrections are positive tree-level corrections to and
negative fermion-loop corrections to , which require that the scale
for the global symmetry breaking be TeV, depending on the top-quark
mixing parameter and the extra gauge couplings. In addition, the loop
corrections to contain a divergence that must be absorbed into the
coefficient of a new operator in the theory. The finite part of this
correction, however, is negligible.Comment: 28 pages, 16 figures, RevTeX forma
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