726 research outputs found
Pseudo Goldstones at Future Colliders from the Extended Bess Model
We consider the production of the lightest pseudo-Goldstone bosons at future
colliders through the vector resonances predicted by the extended BESS model,
which consists of an effective lagrangian parametrization with dynamical
symmetry breaking, describing scalar, vector and axial-vector bound states in a
rather general framework. We find that the detection of pseudo-Goldstone pairs
at LHC requires a careful evaluation of backgrounds. For e+e- collisions in the
TeV range the backgrounds can be easily reduced and the detection of
pseudo-Goldstone pairs is generally easier.Comment: 17 pages and 12 figures (included as a uuencoded tar file), LaTeX
(style article), UGVA-DPT 1994/03-84
New vector bosons in the electroweak sector: a renormalizable model with decoupling
A linear realization of a model of dynamical electroweak symmetry breaking
describing additional heavy vector bosons is proposed. The model is a SU(2)_L x
U(1) x SU(2)_L' x SU(2)_R' gauge theory, breaking at some high scale u to
SU(2)_weak x U(1)_Y and breaking again in the standard way at the electroweak
scale v to U(1)_(em). The model is renormalizable and reproduces the Standard
Model in the limit u\to infinity. This decoupling property is shown to hold
also at the level of radiative corrections by computing, in particular, the
epsilon parameters.Comment: 39 pages, 16 Figures, Late
An Extension of the Electroweak Model with Decoupling at Low Energy
We present a renormalizable model of electroweak interactions containing an
extra symmetry. The masses of the corresponding
gauge bosons and of the associated Higgs particles can be made heavy by tuning
a convenient vacuum expectation value. According to the way in which the heavy
mass limit is taken we obtain a previously considered non-linear model
(degenerate BESS) which, in this limit, decouples giving rise to the Higgsless
Standard Model (SM). Otherwise we can get a model which decouples giving the
full SM. In this paper we argue that in the second limit the decoupling holds
true also at the level of radiative corrections. Therefore the model discussed
here is not distinguishable from the SM at low energy. Of course the two models
differ deeply at higher energies.Comment: 13+2 pages, LaTe
An alternative model for the electroweak symmetry breaking sector and its signature in future e-gamma colliders
We perform a preliminary study of the deviations from the Standard Model
prediction for the cross section for the process . We work in the context of a higgsless chiral lagrangian model that
includes an extra vector resonance and an anomalous coupling.
We find that this cross section can provide interesting constraints on the free
parameters of the model once it is measured in future colliders.Comment: LaTex , 14 pages, 5 figures not included but available as postscript
files upon request, NUB-3086/94-T
Tests for a Strong Electroweak Sector at Future e^+e^- High Energy Colliders
The study of the scattering at high energy of the gauge bosons W and Z, in
particular longitudinally polarized W and Z, can clarify the mechanism of
spontaneous symmetry breaking in the Standard Model of the electroweak
interactions. Different models of strong electroweak sector, based on the
effective lagrangian approach are briefly reviewed. They include models with no
resonance, with scalar resonance, additional vector and axial-vector
resonances. The effective Lagrangians are derived from the chiral symmetry of
the symmetry breaking sector. Limits on these models from existing
measurements, mainly LEP and Tevatron, are considered. We study also direct and
indirect effects of the new interactions at high energy future e^+e^- linear
colliders, through WW scattering and the direct production of these new vector
gauge bosons.Comment: 74 pages, 19 figures and 4 tables included, Latex, uses epsf, to
appear in La Rivista del Nuovo Cimento, some minor change
Indirect effects of new resonances at future linear colliders
In this paper we consider a general invariant
Lagrangian describing scalar, vector and axial-vector resonances. By expanding
the WW and the ZZ scattering amplitude up to the fourth order in the external
momenta we can compare the parameters of our Lagrangian with the ones used in
the effective chiral Lagrangian formalism. In the last approach there has been
a recent study of the fusion processes at future e^+e^- colliders at energies
above 1 TeV. We use these results to put bounds on the parameter space of our
model and to show that for the case of vector resonances the bounds obtained
from the annihilation channel in fermion pairs are by far more restrictive,
already at energies of the order of 500 GeV.Comment: 14 pages, Latex, 1 fi
Heating (Gapless) Color-Flavor Locked Quark Matter
We explore the phase diagram of neutral quark matter at high baryon density
as a function of the temperature T and the strange quark mass Ms. At T=0, there
is a sharp distinction between the insulating color-flavor locked (CFL) phase,
which occurs where Ms^2/mu < 2 Delta, and the metallic gapless CFL phase, which
occurs at larger Ms^2/mu. Here, mu is the chemical potential for quark number
and Delta is the gap in the CFL phase. We find this distinction blurred at
nonzero T, as the CFL phase undergoes an insulator-to-metal crossover when it
is heated. We present an analytic treatment of this crossover. At higher
temperatures, we map out the phase transition lines at which the gap parameters
Delta_1, Delta_2 and Delta_3 describing ds-pairing, us-pairing and ud-pairing
respectively, go to zero in an NJL model. For small values of Ms^2/mu, we find
that Delta_2 vanishes first, then Delta_1, then Delta_3. We find agreement with
a previous Ginzburg-Landau analysis of the form of these transitions and find
quantitative agreement with results obtained in full QCD at asymptotic density
for ratios of coefficients in the Ginzburg-Landau potential. At larger Ms^2/mu,
we find that Delta_1 vanishes first, then Delta_2, then Delta_3. Hence, we find
a "doubly critical'' point in the (Ms^2/mu,T)-plane at which two lines of
second order phase transitions (Delta_1->0 and Delta_2->0) cross. Because we do
not make any small-Ms approximation, if we choose a relatively strong coupling
leading to large gap parameters, we are able to pursue the analysis of the
phase diagram all the way up to such large values of Ms that there are no
strange quarks present.Comment: 24 pages; 22 figures; typos in labelling of Figs. 7, 20 correcte
A linear moose model with pairs of degenerate gauge boson triplets
The possibility of the existence of a strongly interacting electroweak
symmetry breaking sector, as opposed to the weakly interacting light Higgs of
the Standard Model, is not yet ruled out by experiments. In this paper we make
an extensive study of a deconstructed model (or ``moose'' model) providing a
possible effective description of such a strong symmetry breaking sector, and
show its compatibility with experimental data for a wide portion of the model
parameters space. The model is a direct generalization of the previously
proposed D-BESS model.Comment: Latex file, 17 pages, 2 figures, published versio
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